Available-for-Sale and Held-to-Maturity Securities (Schedule of Amortized Cost and Fair Values of the Available for Sale Securities and Held to Maturity Securities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Available-for-Sale and Held-to-Maturity Securities
Available-for-sale securities, Estimated fair value	$ 1,214,141	$ 1,013
Held-to-maturity Securities, Amortized cost	$ 190,484	$ 53

Available-for-Sale and Held-to-Maturity Securities (Schedule of Amortized Cost and Fair Values of the Available for Sale Securities and Held to Maturity Securities) (Details) (USD $)
In Thousands, unless otherwise specified

Dec. 31, 2011

Dec. 31, 2010

Available-for-Sale and Held-to-Maturity Securities

Available-for-sale securities, Estimated fair value

$ 1,214,141

$ 1,013

Held-to-maturity Securities, Amortized cost

$ 190,484

$ 53

- Definition

For an unclassified balance sheet, this item represents investments in debt and equity securities which are categorized neither as held-to-maturity nor trading.

+ References

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+ Details

- Definition

For an unclassified balance sheet, this item represents investments in debt securities which are categorized as held-to-maturity. The held-to-maturity category is for those securities that the entity has the positive intent and ability to hold until maturity.

+ References

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+ Details