Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 42,534	$ 46,672
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit losses	20,000	4,500
Depreciation and amortization	11,060	12,268
(Recovery of) addition to valuation allowance on mortgage servicing rights, net	909	243
Amortization of mortgage servicing rights	2,874	3,179
Amortization of other intangible assets	504	801
Amortization and accretion on earning assets, funding, and other, net	10,692	9,863
Tax impact of stock based compensation	162	638
Gain on sales of investment securities, net	(3,098)	0
Gain on sales of assets and impairment write-downs, net	(524)	(833)
Gain on mortgage banking activities, net	(3,106)	(3,141)
Mortgage loans originated and acquired for sale	(193,849)	(268,296)
Proceeds from sales of mortgage loans held for sale	221,764	238,399
(Increase) decrease in interest receivable	(5,180)	(2,186)
Increase (decrease) in interest payable	(6,121)	(948)
Commercial loans held for sale	(30,089)	0
Other, net	(46,160)	(29,848)
Net cash provided by operating activities	22,372	11,311
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in loans	(531,891)	(368,794)
Purchases of:
Available for sale securities	(182,895)	(202,615)
Held to maturity securities	(28,570)	(36,788)
Federal Home Loan Bank and Federal Reserve Bank stocks	(34,613)	(115)
Premises, equipment, and software, net of disposals	(70,685)	(13,944)
Other assets	(1,226)	(1,207)
Proceeds from:
Sales of available for sale securities	119,379	289
Prepayments, calls, and maturities of available for sale investment securities	180,458	282,835
Prepayments, calls, and maturities of held to maturity investment securities	15,029	5,155
Sales, prepayments, calls, and maturities of other assets	9,566	0
Net cash (paid) received in acquisition	(685)	1,202
Net cash used in investing activities	(526,133)	(333,982)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase (decrease) in deposits	(322,205)	1,088,088
Net increase (decrease) in short-term funding	582,992	(405,751)
Repayment of long-term funding	(430,010)	(500,009)
Proceeds from issuance of long-term funding	615,000	0
Proceeds from issuance of common stock for stock-based compensation plans	2,205	6,236
Purchase of preferred stock	(1,092)	0
Purchase of common stock returned to authorized but unissued	(20,007)	(30,000)
Purchase of treasury stock	(2,792)	(4,105)
Cash dividends on common stock	(16,409)	(15,280)
Cash dividends on preferred stock	(2,198)	(1,228)
Net cash provided by financing activities	405,484	137,951
Net increase (decrease) in cash and cash equivalents	(98,277)	(184,720)
Cash and cash equivalents at beginning of period	473,685	1,032,067	$ 1,032,067
Cash and cash equivalents at end of period	375,408	847,347	$ 473,685
Supplemental disclosures of cash flow information:
Cash paid for interest	28,041	19,643
Cash paid for income taxes	1,167	0
Loans and bank premises transferred to other real estate owned	3,160	2,104
Capitalized mortgage servicing rights	1,856	3,010
Fair value of assets acquired, including cash and cash equivalents	522	5,160
Fair value ascribed to goodwill and intangible assets	4,119	51,221
Fair value of liabilities assumed	1,423	12,851
Common stock issued in acquisition	$ 0	$ 43,530