Consolidated Statements of Cash Flows - USD ($)	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Operating activities:
Net income	$ 32,984,000	$ 35,862,000
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for probable loan losses	9,134,000	2,377,000
Specific reserve, other real estate owned	47,000
Depreciation of bank premises and equipment	6,180,000	6,226,000
Gain on sale of bank premises and equipment	(22,000)	(91,000)
Loss (gain) on sale of other real estate owned	40,000	(28,000)
Accretion of investment securities discounts	(121,000)	(444,000)
Amortization of investment securities premiums	6,132,000	7,217,000
Investment securities transactions, net	133,000	1,000
Impairment charges on available for sale securities	124,000	227,000
Amortization of identified intangible assets	32,000	119,000
Stock based compensation expense	285,000	292,000
Earnings from affiliates and other investments	(3,223,000)	(3,286,000)
Deferred tax expense (benefit)	1,250,000	(1,415,000)
Decrease in accrued interest receivable	2,022,000	1,134,000
Decrease in other assets	4,275,000	1,273,000
Decrease in other liabilities	7,100,000	17,319,000
Net cash provided by operating activities	66,372,000	66,783,000
Investing activities:
Proceeds from maturities of securities		1,075,000
Proceeds from sales and calls of available for sale securities	38,661,000	6,290,000
Purchases of available for sale securities	(319,660,000)	(238,290,000)
Principal collected on mortgage-backed securities	180,342,000	201,856,000
Net increase in loans	(159,000)	(102,699,000)
Purchases of other investments	(759,000)	(550,000)
Distributions from other investments	4,162,000	343,000
Purchases of bank premises and equipment	(4,941,000)	(7,806,000)
Proceeds from sales of bank premises and equipment	1,354,000	744,000
Proceeds from sales of other real estate owned	22,000	3,831,000
Net cash used in investing activities	(100,978,000)	(135,206,000)
Financing activities:
Net increase in non-interest bearing demand deposits	27,029,000	108,597,000
Net increase in savings and interest bearing demand deposits	97,067,000	113,714,000
Net decrease in time deposits	(46,616,000)	(12,014,000)
Net (decrease) increase in securities sold under repurchase agreements	(43,510,000)	15,055,000
Net decrease in other borrowed funds	(6,100,000)	(132,487,000)
Purchase of treasury stock	(7,959,000)	(1,245,000)
Proceeds from stock transactions	112,000	53,000
Net cash provided by financing activities	20,023,000	91,673,000
(Decrease) increase in cash and cash equivalents	(14,583,000)	23,250,000
Cash and cash equivalents at beginning of period	273,053,000	255,146,000
Cash and cash equivalents at end of period	258,470,000	278,396,000
Supplemental cash flow information:
Interest paid	11,132,000	11,549,000
Income taxes paid	100,000	50,000
Non-cash investing and financing activities:
Dividends declared, not yet paid on common stock	19,123,000	19,258,000
Net transfer from loans to other real estate owned	$ 1,161,000	$ 2,248,000