Investment Securities (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Investment securities available for sale:
Amortized Cost	$ 4,775,400	$ 6,011,976
Gross unrealized gains	165,746	135,189
Gross unrealized losses	(3,663)	(45,824)
Fair value	4,937,483	6,101,341
US Treasury Securities
Investment securities available for sale:
Amortized Cost	1,000	1,199
Gross unrealized gains	1	9
Gross unrealized losses	0	0
Fair value	1,001	1,208
Federal agency securities
Investment securities available for sale:
Amortized Cost	24,031	29,791
Gross unrealized gains	18	1
Gross unrealized losses	0	(25)
Fair value	24,049	29,767
Obligations of state and political subdivisions (municipal securities)
Investment securities available for sale:
Amortized Cost	797,691	829,058
Gross unrealized gains	49,583	14,894
Gross unrealized losses	(28)	(5,350)
Fair value	847,246	838,602
Residential mortgage-related securities
Investment securities available for sale:
Amortized Cost	3,674,696	4,831,481
Gross unrealized gains	112,357	117,530
Gross unrealized losses	(1,463)	(38,514)
Fair value	3,785,590	4,910,497
Commercial mortgage-related securities
Investment securities available for sale:
Amortized Cost	16,647	7,604
Gross unrealized gains	1,896	149
Gross unrealized losses	0	0
Fair value	18,543	7,753
Asset-backed securities
Investment securities available for sale:
Amortized Cost	188,439	299,459
Gross unrealized gains	0	3
Gross unrealized losses	(707)	(621)
Fair value	187,732	298,841
Other securities (debt and equity)
Investment securities available for sale:
Amortized Cost	72,896	13,384
Gross unrealized gains	1,891	2,603
Gross unrealized losses	(1,465)	(1,314)
Fair value	$ 73,322	$ 14,673

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.

+ References+ Details

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.

+ References+ 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