Consolidated Statements of Cash Flows - USD ($)	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Operating activities:
Net income	$ 32,004,000	$ 32,984,000
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for probable loan losses	1,700,000	9,134,000
Specific reserve, other real estate owned	45,000	47,000
Depreciation of bank premises and equipment	6,227,000	6,180,000
Gain on sale of bank premises and equipment	(15,000)	(22,000)
(Gain) loss on sale of other real estate owned	(4,000)	40,000
Accretion of investment securities discounts	(120,000)	(121,000)
Amortization of investment securities premiums	7,021,000	6,132,000
Investment securities transactions, net	(927,000)	133,000
Impairment charges on available for sale securities		124,000
Amortization of identified intangible assets	25,000	32,000
Stock based compensation expense	268,000	285,000
Earnings from affiliates and other investments	(2,890,000)	(3,223,000)
Deferred tax expense	229,000	1,250,000
Increase in accrued interest receivable	2,047,000	2,022,000
Decrease in other assets	3,794,000	4,275,000
Net increase in other liabilities	14,990,000	7,100,000
Net cash provided by operating activities	64,394,000	66,372,000
Investing activities:
Proceeds from sales and calls of available for sale securities	121,549,000	38,661,000
Purchases of available for sale securities	(385,594,000)	(319,660,000)
Principal collected on mortgage-backed securities	187,386,000	180,342,000
Net increase in loans	(46,999,000)	(159,000)
Purchases of other investments	(2,903,000)	(759,000)
Distributions from other investments	4,557,000	4,162,000
Purchases of bank premises and equipment	(3,962,000)	(4,941,000)
Proceeds from sales of bank premises and equipment	205,000	1,354,000
Proceeds from sales of other real estate owned	681,000	22,000
Net cash used in by investing activities	(125,080,000)	(100,978,000)
Financing activities:
Net increase in non-interest bearing demand deposits	197,317,000	27,029,000
Net increase in savings and interest bearing demand deposits	82,579,000	97,067,000
Net decrease in time deposits	(25,667,000)	(46,616,000)
Net decrease in securities sold under repurchase agreements	(195,208,000)	(43,510,000)
Net increase (decrease) in other borrowed funds	29,625,000	(6,100,000)
Purchase of treasury stock	(97,000)	(7,959,000)
Proceeds from stock transactions	744,000	112,000
Net cash provided by financing activities	89,293,000	20,023,000
Increase (decrease) in cash and cash equivalents	28,607,000	(14,583,000)
Cash and cash equivalents at beginning of period	269,198,000	273,053,000
Cash and cash equivalents at end of period	297,805,000	258,470,000
Supplemental cash flow information:
Interest paid	10,411,000	11,132,000
Income taxes paid		100,000
Non-cash investing and financing activities:
Net transfer from loans to other real estate owned	9,000	1,161,000
Dividends declared, not yet paid on common stock	$ 21,793,000	$ 19,123,000