Consolidated Statements of Cash Flows (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Operating activities:
Net income	$ 28,069	$ 31,687
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for probable loan losses	7,419	5,285
Specific reserve, other real estate owned	(70)	427
Depreciation of bank premises and equipment	6,625	6,927
(Gain) loss on sale of bank premises and equipment	(21)	30
Gain on sale of other real estate owned	(39)	(232)
Accretion of investment securities discounts	(894)	(755)
Amortization of investment securities premiums	11,204	6,435
Investment securities transactions, net	(9,601)	(1,172)
Impairment charges on available-for-sale investment securities	310	186
Amortization of identified intangible assets	1,137	1,137
Stock based compensation expense	114	131
Earnings from affiliates and other investments	(4,702)	(5,050)
Deferred tax (benefit) expense	(2,098)	1,091
Decrease in accrued interest receivable	2,650	2,352
Net decrease (increase) in other assets	8,926	(113)
Net increase in other liabilities	4,404	11,629
Net cash provided by operating activities	53,433	59,995
Investing activities:
Proceeds from maturities of securities		200
Proceeds from sales and calls of available for sale securities	178,124	17,331
Purchases of available for sale securities	(217,214)	(272,091)
Principal collected on mortgage-backed securities	396,105	306,652
Net (increase) decrease in loans	(59,937)	78,532
Purchases of other investments	(512)	(150)
Distributions of other investments	9,878	10,396
Purchases of bank premises and equipment	(6,166)	(9,566)
Proceeds from sales of other real estate owned	4,410	11,099
Proceeds from sale of bank premises and equipment	21	514
Net cash provided by investing activities	304,709	142,917
Financing activities:
Net increase in non-interest bearing demand deposits	146,577	136,582
Net increase in savings and interest bearing demand deposits	1,413	215,514
Net (decrease) increase in time deposits	(118,660)	19,627
Net (decrease) increase in securities sold under repurchase agreements	(74,092)	13,805
Net decrease in other borrowed funds	(361,534)	(296,033)
Purchases of treasury stock		(558)
Proceeds from stock transactions	13	10
Payments of dividends on preferred stock		(2,700)
Net cash (used in) provided by financing activities	(406,283)	86,247
(Decrease) increase in cash and cash equivalents	(48,141)	289,159
Cash and cash equivalents at beginning of period	283,100	261,885
Cash and cash equivalents at end of period	234,959	551,044
Supplemental cash flow information:
Interest paid	15,590	21,493
Income taxes paid	5,000	50
Non-cash investing and financing activities:
Accrued dividends, preferred shares		1,350
Dividends declared, not yet paid	13,439	13,450
Net transfer from loans to other real estate owned	5,788	28,765
Purchases of available-for-sale securities not yet settled	$ 37,545	$ 26,195