Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES:
Net income	$ 46,003	$ 47,569
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of investment premiums, net	6,878	4,602
Loss (gain) on sale of investment securities, net	2	(696)
Loss (gain) on sale of other real estate owned, net	15	(34)
Valuation adjustment on other real estate owned	67	1,423
Provision for loan and lease losses	11,672	4,823
Change in cash surrender value of bank owned life insurance	(2,104)	(2,208)
Depreciation, amortization and accretion	14,862	14,828
Loss on sale of premises and equipment	0	299
Additions to residential mortgage servicing rights carried at fair value	(7,041)	(5,980)
Change in fair value of residential mortgage servicing rights carried at fair value	7,670	20,625
Change in junior subordinated debentures carried at fair value	1,396	1,460
Stock-based compensation	2,804	3,227
Net increase in trading account assets	(277)	(205)
Gain on sale of loans	(22,746)	(33,340)
Change in loans held for sale carried at fair value	(4,885)	(4,861)
Origination of loans held for sale	(754,715)	(764,076)
Proceeds from sales of loans held for sale	795,837	759,893
Goodwill impairment	0	142
Change in other assets and liabilities:
Net decrease (increase) in other assets	19,235	(19,844)
Net (decrease) increase in other liabilities	(54,791)	15,193
Net cash provided by operating activities	59,882	42,840
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchases of investment securities available for sale	(672,148)	(96,603)
Proceeds from investment securities available for sale	127,195	103,629
Proceeds from investment securities held to maturity	124	111
Purchases of restricted equity securities	(1)	(600)
Redemption of restricted equity securities	7	4
Net change in loans and leases	(360,236)	(505,995)
Proceeds from sales of loans	25,259	151,466
Net change in premises and equipment	(6,937)	(10,099)
Proceeds from bank owned life insurance death benefits	0	25
Proceeds from sales of other real estate owned	927	2,461
Net cash used in investing activities	(885,810)	(355,601)
CASH FLOWS FROM FINANCING ACTIVITIES:
Net increase in deposit liabilities	146,619	456,620
Net (decrease) increase in securities sold under agreements to repurchase	(48,668)	20,643
Proceeds from term debt borrowings	100,000	115,000
Repayment of term debt borrowings	(100,000)	(100,000)
Dividends paid on common stock	(35,243)	(35,281)
Proceeds from stock options exercised	230	513
Repurchase and retirement of common stock	(1,796)	(5,539)
Net cash provided by financing activities	61,142	451,956
Net (decrease) increase in cash and cash equivalents	(764,786)	139,195
Cash and cash equivalents, beginning of period	1,449,432	773,725
Cash and cash equivalents, end of period	684,646	912,920
SUPPLEMENTAL DISCLOSURES OF CASH FLOW INFORMATION:
Interest	18,161	18,313
Income taxes	8,281	8,165
SUPPLEMENTAL DISCLOSURE OF NONCASH INVESTING AND FINANCING ACTIVITIES:
Change in unrealized gains on investment securities available for sale, net of taxes	2,539	18,975
Cash dividend declared on common stock and payable after period-end	35,264	35,247
Transfer of loans to loans held for sale	0	255,976
Change in GNMA mortgage loans recognized due to repurchase option	(5,603)	(5,021)
Transfer of loans to other real estate owned	789	2,210
Transfers from other real estate owned to loans due to internal financing	0	256
Receivable from BOLI death benefits	$ 0	$ 372