part ii / item 8 Changes to goodwill are as follows: (in thousands) December 31, 2012 2011 Balance at beginning of period $820,824 $810,285 Additions — 10,900 Disposals (13,966) — Adjustments to purchase price allocations — 3,932 Currency translation 6,934 (4,293) Balance at end of period $ 813,792 $820,824 For the year ended December 31, 2012, the disposals represent goodwill associated with the Company’s divested businesses. See discussion in Note 2, “Discontinued Operations” for further details. For the year ended December 31, 2011, the additions to goodwill represent the initial purchase price allocation related to WTA, and the adjustments to purchase price allocations pertain to the December 2010 acquisition of Money Controls and the February 2010 acquisition of Merrimac Industries, Inc. (“Merrimac”). For the year ended December 31, 2012, the disposals represent intangible assets associated with the Company’s divested busi- nesses. See discussion in Note 2, “Discontinued Operations” for further details. For the year ended December 31, 2011, the additions relate to the December 2010 acquisition of Money Controls and the July 2011 acquisition of WTA. As of December 31, 2012, the Company had $125.9 million of net intangible assets, of which $31.2 million were intangibles with indefinite useful lives, consisting of trade names. The Company amortizes the cost of other intangibles over their estimated useful lives unless such lives are deemed indefinite. Intangibles with indefinite useful lives are tested annually for impairment, or when events or changes in circumstances indicate the potential for impairment. If the carrying amount of the intangibles with indef- inite useful lives exceeds the fair value, the intangible asset is writ- ten down to its fair value. Fair value is calculated using discounted cash flows. 41 Changes to intangible assets are as follows: (in thousands) December 31, 2012 2011 Balance at beginning of period, net of accumulated amortization $146,227 $162,636 Additions — 5,980 Disposals (3,789) — Amortization expense (16,907) (21,646) Currency translation and other 382 (743) Balance at end of period, net of accumulated amortization $125,913 $146,227 A summary of intangible assets follows: Weighted Average Amortization Period of Finite Lived Assets (in years) December 31, 2012 December 31, 2011 (in thousands) Gross Asset Accumulated Amortization Net Gross Asset Accumulated Amortization Net Intellectual property rights 18.9 $ 88,614 $ 47,202 $ 41,412 $ 89,619 $ 46,286 $ 43,333 Customer relationships and backlog 11.6 140,250 73,630 66,620 146,291 66,256 80,035 Drawings 37.9 11,149 9,850 1,299 11,824 10,423 1,401 Other 14.1 51,093 34,511 16,582 52,155 30,697 21,458 Total 14.0 $291,106 $165,193 $125,913 $299,889 $153,662 $146,227 Amortization expense for these intangible assets is currently esti- mated to be approximately $16.5 million in 2013, $14.5 million in 2014, $12.7 million in 2015, $11.9 million in 2016 and $39.1 million in 2017 and thereafter. Valuation of Long-Lived Assets The Company reviews its long- lived assets for impairment whenever events or changes in circum- stances indicate the carrying amount of an asset may not be recoverable. Examples of events or changes in circumstances could include, but are not limited to, a prolonged economic downturn, current period operating or cash flow losses combined with a his- tory of losses or a forecast of continuing losses associated with the use of an asset or asset group, or a current expectation that an asset or asset group will be sold or disposed of before the end of its pre- viously estimated useful life. Recoverability is based upon projec- tions of anticipated future undiscounted cash flows associated with the use and eventual disposal of the long-lived asset (or asset group), as well as specific appraisal in certain instances. Reviews occur at the lowest level for which identifiable cash flows are largely independent of cash flows associated with other long-lived assets or asset groups. If the future undiscounted cash flows are less than the carrying value, then the long-lived asset is considered impaired and a loss is recognized based on the amount by which the carrying amount exceeds the estimated fair value. Judgments that the Com- pany makes which impact these assessments relate to the expected useful lives of long-lived assets and its ability to realize any undis- counted cash flows in excess of the carrying amounts of such assets, and are affected primarily by changes in the expected use of the assets, changes in technology or development of alternative assets, changes in economic conditions, changes in operating performance and changes in expected future cash flows. Since judgment is involved in determining the fair value of long-lived assets, there is risk that the carrying value of our long-lived assets may require adjustment in future periods.