Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Operating Activities
Net income	$ 147,861	$ 112,989
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	18,934	16,070
Depreciation, amortization, and accretion, net	29,334	28,506
Deferred income tax expense	70,484	61,283
Decrease in trading account assets	6,269	4,096
Originations of mortgage loans held for sale	(325,094)	(320,304)
Proceeds from sales of mortgage loans held for sale	323,861	299,186
Gain on sales of mortgage loans held for sale, net	(7,049)	(6,946)
Increase in other assets	(14,525)	(33,152)
(Decrease) increase in other liabilities	(9,667)	13,162
Investment securities gains, net	(7,667)	(67)
Losses and write-downs on other real estate, net	2,856	6,089
Decrease in fair value of private equity investments, net	3,166	278
Losses and write-downs on other assets held for sale, net	0	7,902
Loss on early extinguishment of debt, net	0	4,735
Share-based compensation expense	6,838	6,849
Net cash provided by operating activities	245,601	200,676
Investing Activities
Net decrease (increase) in interest earning deposits with banks	12,708	(7,154)
Net decrease (increase) in federal funds sold and securities purchased under resale agreements	11,213	(7,866)
Net decrease (increase) in interest bearing funds with Federal Reserve Bank	58,942	(74,519)
Proceeds from maturities and principal collections of investment securities available for sale	313,902	443,128
Proceeds from sales of investment securities available for sale	338,381	243,609
Purchases of investment securities available for sale	(748,754)	(623,046)
Proceeds from sales of loans	10,747	7,739
Proceeds from sales of other real estate	5,492	16,282
Net increase in loans	(612,309)	(660,778)
Purchases of bank-owned life insurance policies	(75,000)	0
Net increase in premises and equipment	(15,386)	(16,769)
Proceeds from sales of other assets held for sale	3,158	296
Net cash used in investing activities	(696,906)	(679,078)
Financing Activities
Net increase in demand and savings deposits	367,450	595,342
Net increase in certificates of deposit	202,927	87,466
Net (decrease) increase in federal funds purchased and securities sold under repurchase agreements	(9,320)	70,154
Repayments on long-term debt	(1,128,591)	(1,455,067)
Proceeds from issuance of long-term debt	1,075,000	1,400,000
Dividends paid to common shareholders	(18,349)	(30,015)
Dividends paid to preferred shareholders	(5,119)	(5,119)
Stock options exercised	2,504	2,035
Repurchases of common stock	(45,349)	(171,547)
Restricted stock activity	(7,810)	(4,605)
Net cash provided by financing activities	433,343	488,644
(Decrease) increase in cash and cash equivalents	(17,962)	10,242
Cash and cash equivalents at beginning of period	395,175	367,092
Cash and cash equivalents at end of period	377,213	377,334
Supplemental Cash Flow Information
Income tax payments, net	8,768	5,849
Interest paid	67,007	64,424
Non-cash Activities
Premises and equipment transferred to other assets held for sale	0	18,677
Other assets held for sale transferred to premises and equipment	4,450	0
Loans foreclosed and transferred to other real estate	5,516	8,631
Loans transferred to other loans held for sale at fair value	10,584	7,314
Dividends declared on common stock during the period but paid after period-end	$ 18,349	$ 0