Debt Security Investments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Amortized cost, gross unrealized gains, gross unrealized losses and fair values of debt security investments
Amortized Cost	$ 3,486
Total debt security investments, Fair Value	3,499
U.S. Treasury Securities [Member]
Amortized cost, gross unrealized gains, gross unrealized losses and fair values of debt security investments
Amortized Cost	3,486	36,950
Gross Unrealized Gains	13
Gross Unrealized Losses		6
Total debt security investments, Fair Value	$ 3,499	$ 36,944

Amount of debt securities categorized neither as held-to-maturity nor trading.

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+ Details

- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

+ References+ Details