Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 77,669	$ 46,003
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of investment premiums, net	5,907	6,878
Loss on sale of investment securities, net	0	2
(Gain) loss on sale of other real estate owned, net	(43)	15
Valuation adjustment on other real estate owned	5	67
Provision for loan and lease losses	13,656	11,672
Change in cash surrender value of bank owned life insurance	(2,105)	(2,104)
Depreciation, amortization and accretion	13,943	14,862
Gain on sale of premises and equipment	(1,341)	0
Additions to residential mortgage servicing rights carried at fair value	(6,530)	(7,041)
Change in fair value of residential mortgage servicing rights carried at fair value	(5,079)	7,670
Gain on redemption of junior subordinated debentures at amortized cost	(1,043)	0
Change in junior subordinated debentures carried at fair value	0	1,396
Stock-based compensation	1,829	2,804
Net increase in equity and other account assets	(107)	(277)
Gain on sale of loans, net	(14,508)	(22,746)
Change in loans held for sale carried at fair value	306	(4,885)
Origination of loans held for sale	(687,226)	(754,715)
Proceeds from sales of loans held for sale	659,977	795,837
Change in other assets and liabilities:
Net decrease in other assets	10,116	19,235
Net increase (decrease) in other liabilities	1,814	(54,791)
Net cash provided by operating activities	67,240	59,882
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of investment securities available for sale	(89,145)	(672,148)
Proceeds from investment securities available for sale	107,908	127,195
Proceeds from investment securities held to maturity	172	124
Purchases of restricted equity securities	0	(1)
Redemption of restricted equity securities	7	7
Net change in loans and leases	(274,731)	(360,236)
Proceeds from sales of loans	21,629	25,259
Net change in premises and equipment	(462)	(6,937)
Proceeds from sales of other real estate owned	161	927
Net cash used in investing activities	(234,461)	(885,810)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in deposit liabilities	158,771	146,619
Net decrease in securities sold under agreements to repurchase	(2,315)	(48,668)
Proceeds from term debt borrowings	50,000	100,000
Repayment of term debt borrowings	(50,513)	(100,000)
Repayment of junior subordinated debentures at amortized cost	(10,598)	0
Dividends paid on common stock	(39,634)	(35,243)
Proceeds from stock options exercised	759	230
Repurchase and retirement of common stock	(4,340)	(1,796)
Net cash provided by financing activities	102,130	61,142
Net decrease in cash and cash equivalents	(65,091)	(764,786)
Cash and cash equivalents, beginning of period	634,280	1,449,432
Cash and cash equivalents, end of period	569,189	684,646
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Interest	23,489	18,161
Income taxes	11,440	8,281
SUPPLEMENTAL DISCLOSURE OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Change in unrealized gains on investment securities available for sale, net of taxes	(31,419)	2,539
Change in unrealized gains on junior subordinated debentures carried at fair value, net of taxes	(1,253)	0
Junior subordinated debentures, at fair value, cumulative effect adjustment	9,710	0
Cash dividend declared on common stock and payable after period-end	44,016	35,264
Change in GNMA mortgage loans recognized due to repurchase option	(6,152)	(5,603)
Transfer of loans to other real estate owned	1,444	789
Receivable from BOLI death benefits	$ 1,224	$ 0