Investment Securities - Debt Maturities (Details) (Investment Securities, USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Investment Securities
Available-for-sale Securities, Debt Maturities, Amortized Cost Basis, Fiscal Year Maturity [Abstract]
Available-for-sale Securities, Due within one year, Amortized Cost	$ 1,370,334
Available-for-sale Securities, Due after one year through five years, Amortized Cost	168,249
Available-for-sale Securities, Due after five years through ten years, Amortized Cost	435,609
Available-for-sale Securities, Due after ten years, Amortized Cost	670,328
Available-for-sale Securities, Amortized Cost	2,644,520	2,203,928
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
Available-for-sale Securities, Due within one year, Fair Value	1,370,517
Available-for-sale Securities, Due after one year through five years, Fair Value	169,159
Available-for-sale Securities, Due after five years through ten years, Fair Value	425,640
Available-for-sale Securities, Due after ten years, Fair Value	669,668
Total available-for-sale	$ 2,634,984	$ 2,182,694
Available-for-sale Securities, Debt Maturities, Weighted-Average Yield, Fiscal Year Maturity [Abstract]
Available-for-sale Securities, Due within one year, Weighted-Average Yield	0.63%
Available-for-sale Securities, Due after one year through five years, Weighted-Average Yield	0.90%
Available-for-sale Securities, Due after five years through ten years, Weighted-Average Yield	1.13%
Available-for-sale Securities, Due after ten years, Weighted-Average Yield	2.54%
Available-for-sale Securities, Total Weighted-Average Yield	1.21%

Available-for-sale Securities, Debt Maturities, after Ten Years, Weighted-Average Yield

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Available-for-sale Securities, Debt Maturities, Next Twelve Months, Weighted-Average Yield

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Available-for-sale Securities, Debt Maturities, Year Six Through Ten, Weighted-Average Yield

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Available-for-sale Securities, Debt Maturities, Year Two Through Five, Weighted-Average Yield

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This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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Amount of available-for-sale debt securities at cost, net of adjustments, maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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Amount of available-for-sale debt securities at fair value maturing in the sixth fiscal year through the tenth fiscal year following the latest fiscal year.

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Amount of available-for-sale debt securities at cost, net of adjustments, maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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Amount of available-for-sale debt securities at fair value maturing in the second fiscal year through the fifth fiscal year following the latest fiscal year.

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Amount of available-for-sale debt securities at cost, net of adjustments, maturing after the tenth fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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Amount of available-for-sale debt securities at fair value maturing after the tenth fiscal year following the latest fiscal year.

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Amount of available-for-sale debt securities at cost, net of adjustments, maturing in the next fiscal year following the latest fiscal year. Adjustments include, but are not limited to, accretion, amortization, collection of cash, previous other-than-temporary impairments (OTTI) recognized in earnings (less any cumulative-effect adjustments, as defined) and fair value hedge accounting adjustments.

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Amount of available-for-sale debt securities at fair value maturing in the next fiscal year following the latest fiscal year.

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- Definition

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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