We receive payment from customers based on a contractual billing schedule and specific performance requirements as established in our contracts. We record billings as accounts receivable when an unconditional right to consideration exists. A contract asset represents revenue recognized in advance of our right to bill the customer under the terms of a contract. A contract liability represents our contractual billings in advance of revenue recognized for a contract. The following table presents opening and closing balances of contract assets and contract liabilities, current and long-term, for the years ended December 31, 2019 and 2018: Contract Balances ( Amounts in thousands) Contract Assets, net (Current) Long-term Contract Assets, net(1) Contract Liabilities (Current) Long-term Contract Liabilities(2) Balance — January 1, 2018 $ 219,361 $ 3,990 $ 178,515 $ 3,925 Revenue recognized that was included in contract liabilities at the beginning of the period — — (123,458) (1,360) Increase due to revenue recognized in the period in excess of billings 846,922 6,668 — — Increase due to billings arising during the period in excess of revenue recognized — — 152,664 (481) Amounts transferred from contract assets to receivables (815,213 ) (2,503 ) — — Currency effects and other, net (22,491) 2,812 (5,263) (714) Balance — December 31, 2018 $ 228,579 $ 10,967 $ 202,458 $ 1,370 Revenue recognized that was included in contract liabilities at the beginning of the period — — (125,274) — Increase due to revenue recognized in the period in excess of billings 835,147 — — — Increase due to billings arising during the period in excess of revenue recognized — — 135,695 290 Amounts transferred from contract assets to receivables (785,279 ) (1,747 ) — — Currency effects and other, net (5,533) 60 3,662 (8) Balance — December 31, 2019 $ 272,914 $ 9,280 $ 216,541 $ 1,652 (1) Included in other assets, net. (2) Included in retirement obligations and other liabilities. On June 29, 2018, pursuant to a plan of sale approved by management, we executed an agreement to divest two FPD locations and associated product lines, including the related assets and liabilities. This transaction did not meet the criteria for classification of assets held for sale as of June 30, 2018 due to a contingency that could have potentially impacted the final terms and/or timing of the divestiture. The sale transaction was completed on August 9, 2018. During the twelve months ended December 31, 2018, we recorded a pre-tax charge of $25.1 million, including a pre- tax charge of $17.4 million in the second quarter of 2018 and a loss on sale of the business of $7.7 million in the third quarter of 2018. The second quarter of 2018 pre-tax charge related to write-downs of inventory and long-lived assets to their estimated fair value, of which $7.7 million was recorded in COS and $9.7 million was recorded in SG&A. The third quarter of 2018 pre-tax charge primarily related to working capital changes since the second quarter of 2018 and net cash transferred at the closing date of $3.7 million. The sale included a manufacturing facility in Germany and a related assembly facility in France. In 2017, net sales related to the business totaled approximately $42 million, although the business produced an operating loss in 2016 and 2015. 70 3. DISPOSITIONS FPD Business Divestiture