Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 56,270	$ 42,534
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	9,000	20,000
Depreciation and amortization	11,505	11,060
Addition to valuation allowance on mortgage servicing rights, net	217	909
Amortization of mortgage servicing rights	2,477	2,874
Amortization of other intangible assets	513	504
Amortization and accretion on earning assets, funding, and other, net	8,215	10,692
Tax impact of stock based compensation	3,486	162
Gain on sales of investment securities, net	0	(3,098)
Asset (gains) losses, net	234	(524)
Gain on mortgage banking activities, net	5,171	(3,106)
Mortgage loans originated and acquired for sale	(101,280)	(193,849)
Proceeds from sales of mortgage loans held for sale	196,578	221,764
Increase in interest receivable	(761)	(5,180)
Decrease in interest payable	(185)	(6,121)
Commercial loans held for sale	(2,155)	(30,089)
Other, net	(19,532)	(46,160)
Net cash provided by operating activities	169,753	22,372
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in loans	(113,051)	(531,891)
Purchases of:
Available for sale securities	(163,442)	(182,895)
Held to maturity securities	(2,655)	(28,570)
Federal Home Loan Bank and Federal Reserve Bank stocks	(58,362)	(34,613)
Premises, equipment, and software, net of disposals	(13,586)	(70,685)
Other assets	(5,433)	(1,226)
Proceeds from:
Sales of available for sale securities	0	119,379
Proceeds from Sale of Federal Home Loan Bank Stock	59,090	0
Prepayments, calls, and maturities of available for sale investment securities	231,019	180,458
Prepayments, calls, and maturities of held to maturity investment securities	22,916	15,029
Sales, prepayments, calls, and maturities of other assets	3,293	9,566
Net cash paid in acquisition	(217)	(685)
Net cash used in investing activities	(40,428)	(526,133)
CASH FLOWS FROM FINANCING ACTIVITIES
Net decrease in deposits	(60,413)	(322,205)
Net increase (decrease) in short-term funding	(11,168)	582,992
Repayment of long-term funding	(8)	(430,010)
Proceeds from issuance of long-term funding	0	615,000
Proceeds from issuance of common stock for stock-based compensation plans	17,940	2,205
Purchase of preferred stock	0	(1,092)
Purchase of common stock returned to authorized but unissued	0	(20,007)
Purchase of treasury stock for tax withholding	(7,743)	(2,792)
Cash dividends on common stock	(18,368)	(16,409)
Cash dividends on preferred stock	(2,330)	(2,198)
Net cash provided by financing activities	(82,090)	405,484
Net increase (decrease) in cash and cash equivalents	47,235	(98,277)
Cash and cash equivalents at beginning of period	642,233	473,685	$ 473,685
Cash and cash equivalents at end of period	689,468	375,408	$ 642,233
Supplemental disclosures of cash flow information:
Cash paid for interest	26,531	28,041
Cash paid for income taxes	1,052	1,167
Loans and bank premises transferred to other real estate owned	921	3,160
Capitalized mortgage servicing rights	1,920	1,856
Loans transferred into held for sale from portfolio, net	13,905	0
Fair value of assets acquired, including cash and cash equivalents	0	522
Fair value ascribed to goodwill and intangible assets	217	4,119
Fair value of liabilities assumed	$ 0	$ 1,423