Parent Company Only Financials (Details 2) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (loss)	$ 178,973	$ 139,699	$ (856)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	43,611	33,628	30,108
(Gain) loss on sales of investment securities, net, and impairment write-downs	(4,261)	1,112	(24,917)
(Gain) loss on sale of assets, net	(12,096)	(12,199)	(12,065)
Net change in other assets and other liabilities	(19,461)	(53,169)	(38,871)
Net cash provided by (used in) operating activities	350,484	309,787	509,422
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from sales of investment securities	299,782	176,267	971,662
Purchase of investment securities	2,131,026	777,309	3,369,225
Purchase of other assets, net of disposals	(5,968)	(3,061)	(15,516)
Net cash provided by (used in) investing activities	(1,633,722)	(472,537)	616,770
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase (decrease) in short-term funding	(187,546)	767,103	520,529
Proceeds from issuance of long-term funding	154,738	432,504	400,000
Repayment of long-term funding	(311,621)	(670,104)	(940,361)
Redemption of preferred stock	0	(525,000)	0
Proceeds from issuance of common stock	0	0	478,358
Proceeds from issuance of preferred stock	0	63,272	0
Purchase of treasury stock	(61,654)	(659)	(830)
Net cash provided by (used in) financing activities	1,404,516	(88,817)	(1,078,722)
Net increase (decrease) in cash and cash equivalents	121,278	(251,567)	47,470
Cash and cash equivalents at beginning of period	616,595	868,162	820,692
Cash and cash equivalents at end of period	737,873	616,595	868,162
Parent Company [Member]
CASH FLOWS FROM OPERATING ACTIVITIES
Net income (loss)	178,973	139,699	(856)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
(Increase) decrease in equity in undistributed net income (loss) of subsidiaries	(33,931)	(154,007)	(21,107)
Depreciation and amortization	132	171	254
(Gain) loss on sales of investment securities, net, and impairment write-downs	(530)	81	799
(Gain) loss on sale of assets, net	1,365	(13)	0
Net change in other assets and other liabilities	142,900	25,356	40,469
Excess tax benefit from stock-based compensation	0	0	0
Capital (contributed to) received from subsidiaries	0	0	(200,000)
Net cash provided by (used in) operating activities	288,909	11,287	(180,441)
CASH FLOWS FROM INVESTING ACTIVITIES
Proceeds from sales of investment securities	49,819	14,667	0
Purchase of investment securities	(186,432)	(75,221)	0
Net cash paid in acquisition of subsidiary's stock	0	0	0
Net (increase) decrease in notes receivable	(225)	391,996	(232,499)
Purchase of other assets, net of disposals	(7,336)	4,977	(5,204)
Net cash provided by (used in) investing activities	(144,174)	336,419	(237,703)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase (decrease) in short-term funding	51,245	0	0
Proceeds from issuance of long-term funding	154,738	432,504	0
Repayment of long-term funding	(211,340)	(170,000)	(30,000)
Redemption of preferred stock	0	(525,000)	0
Proceeds from issuance of common stock	0	0	478,358
Proceeds from issuance of preferred stock	0	63,272	0
Cash dividends	(44,834)	(21,195)	(33,198)
Purchase of treasury stock	(61,654)	(659)	(830)
Net cash provided by (used in) financing activities	(111,845)	(221,078)	414,330
Net increase (decrease) in cash and cash equivalents	32,890	126,628	(3,814)
Cash and cash equivalents at beginning of period	126,835	207	4,021
Cash and cash equivalents at end of period	$ 159,725	$ 126,835	$ 207