December 31, 2010 Carrying  Amount Unrealized  Gain Unrealized  Loss NT$ NT$ NT$ (In Millions) Available-for-sale securities Open-end mutual funds $  1,562  $  14  $  23  Domestic listed stocks 527  236  19  Corporate bonds 102  1  —  2,191  251  42  Held-to-maturity securities Corporate bond 9,868  326  96  Bank debentures 504  1  5  10,372  327  101  $  12,563  $  578  $  143  December 31,  2010  NT$ (In Millions) Due within one year or less $  1,964  Due after one year through four years 8,510  $  10,474  Less than 12 Months 12 Months or Greater Total Fair  Value Unrealized  Losses Fair  Value Unrealized  Losses Fair  Value Unrealized  Losses NT$ NT$ NT$ NT$ NT$ NT$ (In Millions) Open-end-mutual funds $  1,089  $  (23) $  —  $  —  $  1,089  $  (23) Domestic listed stocks 149  (19) 149  (19) Corporate bond 1,986  (96) —  —  1,986  (96) Bank debentures 199  (5) 199  (5) $  3,423  $  (143) $  —  $  —  $  3,423  $  (143) F-76 The following table shows the gross unrealized losses and fair value of the investments with unrealized  losses that are not deemed to be other-than-temporary impaired, aggregated by investment category and  length of time that have been in a continuous unrealized loss position as of December 31, 2010:  The Company’s gross realized gains on the sale of investments for the years ended December 31, 2008,  2009 and 2010 were NT$131 million, NT$553 million and NT$476 million, respectively. The Company’s  gross realized losses on the sale of investments for the years ended December 31, 2008, 2009 and 2010  were NT$1,014 million, NT$695 million and NT$654 million, respectively.  The carrying amounts at December 31, 2010 for debt securities classified as available-for-sale securities  and held-to-maturity by contractual maturity are shown below. 