NOTES TO CONSOLIDATED FINANCIAL STATEMENTS B. INVESTMENTS IN MARKETABLE DEBT SECURITIES  December 31, 2011, 2010 and 2009 (currencies in millions) Marketable debt securities consisted of the following at December 31: The cost of marketable debt securities is adjusted for amortization of premiums and accretion of discounts to  maturity. Amortization, accretion, interest and dividend income and realized gains and losses are included in  investment income. The cost of securities sold is based on the specific identification method. The proceeds from  sales and maturities of marketable securities during 2011 were $1,142.4. Gross realized gains were $3.2, $.7 and $1.2  and gross realized losses were $1.3, $.1 and $.1 for the years ended December 31, 2011, 2010 and 2009, respectively. The fair value of marketable debt securities that have been in an unrealized loss position for 12 months or greater  at December 31, 2011 was $8.0 and the associated unrealized loss was $.1. The Company had no marketable debt  securities in an unrealized loss position for 12 months or greater at December 31, 2010. For the investment securities in gross unrealized loss positions identified above, the Company does not intend to  sell the investment securities, it is more likely than not that the Company will not be required to sell the investment  securities before recovery of the unrealized losses, and the Company expects that the contractual principal and  interest will be received on the investment securities. As a result, the Company recognized no other-than-temporary  impairments during the periods presented. Contractual maturities at December 31, 2011 were as follows: Marketable debt securities included $7.1 and $12.2 of variable-rate demand obligations (VRDOs) at December 31,  2011 and 2010, respectively. VRDOs are debt instruments with long-term scheduled maturities which have interest  rates that reset periodically. AMORTIZED FAIR Maturities:  COST VALUE Within one year  $ 259.7 $ 260.1 One to five years  633.9 642.9 Ten or more years  7.1 7.1 $ 900.7  $ 910.1 AMORTIZED UNREALIZED UNREALIZED FAIR 2011  COST GAINS LOSSES VALUE U.S. tax-exempt securities  $ 291.9 $ 2.6 $ .1 $ 294.4 U.S. corporate securities   27.4  .3  .2  27.5 U.S. government and agency securities  1.9 1.9 Non-U.S. government securities   361.2  6.0  .1  367.1 Non-U.S. corporate securities   148.0  .5  .2  148.3 Other debt securities  70.3 .6 70.9 $ 900.7 $ 10.0 $ .6 $ 910.1 AMORTIZED UNREALIZED UNREALIZED FAIR 2010 COST GAINS LOSSES VALUE U.S. tax-exempt securities  $ 364.9  $  .8  $  .3  $ 365.4 U.S. corporate securities  27.3 .3  27.6 U.S. government and agency securities  2.7 2.7 Non-U.S. corporate securities  37.0 37.0 Other debt securities  17.8 17.8 $ 449.7  $  1.1  $  .3  $ 450.5