Consolidated Statements of Cash Flows - USD ($)	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Operating activities:
Net income	$ 157,402,000	$ 112,201,000
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for probable loan losses	3,212,000	9,096,000
Specific reserve, other real estate owned	3,033,000	330,000
Depreciation of bank premises and equipment	19,097,000	18,936,000
Gain on sale of bank premises and equipment	(293,000)	(30,000)
Gain on sale of other real estate owned	(1,317,000)	(267,000)
Accretion of investment securities discounts	(209,000)	(307,000)
Amortization of investment securities premiums	15,620,000	18,068,000
Investment securities transactions, net	141,000	1,612,000
Unrealized loss on equity securities with readily determinable fair values	312,000
Amortization of identified intangible assets		25,000
Stock based compensation expense	755,000	699,000
Earnings from affiliates and other investments	(12,247,000)	(9,538,000)
Deferred tax expense (benefit)	1,373,000	(26,000)
Decrease (increase) in accrued interest receivable	65,000	(106,000)
(Increase) decrease in other assets	(48,747,000)	6,516,000
Net increase in other liabilities	40,533,000	17,314,000
Net cash provided by operating activities	178,730,000	174,523,000
Investing activities:
Proceeds from maturities of securities	1,075,000
Proceeds from sales and calls of available for sale securities	37,675,000	279,419,000
Proceeds from sales of equity securities with readily determinable fair values	21,607,000
Purchases of available for sale securities	(47,346,000)	(944,241,000)
Principal collected on mortgage backed securities	529,956,000	573,713,000
Net increase in loans	(168,823,000)	(245,019,000)
Purchases of other investments	(34,914,000)	(10,282,000)
Distributions from other investments	2,894,000	349,000
Purchases of bank premises and equipment	(16,256,000)	(10,303,000)
Proceeds from sales of other real estate owned	1,413,000	2,194,000
Proceeds from sales of bank premises and equipment	3,633,000	11,139,000
Net cash provided by (used in) investing activities	330,914,000	(343,031,000)
Financing activities:
Net increase in non-interest bearing demand deposits	188,518,000	86,778,000
Net (decrease) increase in savings and interest bearing demand deposits	(13,938,000)	49,654,000
Net decrease in time deposits	(73,871,000)	(132,980,000)
Net decrease in securities sold under repurchase agreements	(20,002,000)	(126,952,000)
Net (decrease) increase in other borrowed funds	(520,325,000)	334,125,000
Repurchase of outstanding common stock warrant	(29,005,000)
Purchase of treasury stock	(57,000)	(132,000)
Proceeds from stock transactions	1,158,000	1,185,000
Payments of cash dividends - common	(21,815,000)	(21,793,000)
Net cash (used in) provided by financing activities	(489,337,000)	189,885,000
Increase in cash and cash equivalents	20,307,000	21,377,000
Cash and cash equivalents at beginning of period	265,357,000	269,198,000
Cash and cash equivalents at end of period	285,664,000	290,575,000
Supplemental cash flow information:
Interest paid	37,051,000	9,735,000
Income taxes paid	39,715,000	54,442,000
Non-cash investing and financing activities:
Net transfers from loans to other real estate owned	31,609,000	1,538,000
Dividends declared, not yet paid on common stock	$ 27,784,000	$ 21,801,000