Debt Security Investments (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Amortized cost, gross unrealized gains, gross unrealized losses and fair values of debt security investments
Amortized Cost	$ 83,492
US Treasury Securities [Member]
Amortized cost, gross unrealized gains, gross unrealized losses and fair values of debt security investments
Amortized Cost	83,492	33,481
Gross Unrealized Gains
Gross Unrealized Losses	(45)	(2)
Fair Value	$ 83,447	$ 33,479

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