Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 49,438	$ 50,207		$ 145,510	$ 141,771
Adjustments to reconcile net income (loss) to net cash provided by (used in) operating activities:
Provision for credit losses	8,000	1,000		17,500	11,000
Depreciation and amortization				35,788	38,023
Recovery of valuation allowance on mortgage servicing rights, net				(306)	(89)
Amortization of mortgage servicing rights				8,902	8,224
Amortization of other intangible assets	885	990		2,574	2,972
Amortization and accretion on earning assets, funding, and other, net				29,039	21,647
Tax impact of stock based compensation				2,093	1,184
Gain on sales of investment securities, net	(2,796)	(57)		(4,038)	(469)	$ (494)
Gain on sales of assets and impairment write-downs, net	(95)	(4,934)		(3,084)	(6,561)
Gain on mortgage banking activities, net				(15,504)	(11,668)
Mortgage loans originated and acquired for sale				(911,133)	(777,532)
Proceeds from sales of mortgage loans held for sale				941,575	735,565
Pension contributions				0	(21,000)
Increase in interest receivable				(3,404)	(3,301)
Decrease in interest payable				2,642	6,451
Other, net				(3,492)	(2,603)
Net cash provided by operating activities				239,378	130,712
CASH FLOWS FROM INVESTING ACTIVITIES
Net increase in loans				(935,208)	(1,292,718)
Purchases of:
Available for sale securities				(2,075,062)	(808,899)
Held to maturity securities				(207,139)	(126,602)
FHLB stock				(14,279)	(7,626)
Premises, equipment, and software, net of disposals				(36,778)	(35,507)
Other assets				(9,903)	(2,460)
Proceeds from:
Sales of available for sale securities			$ 1,000,000	1,066,957	101,987	102,011
Sales of available for sale securities				42,514	0
Prepayments, calls, and maturities of available for sale securities				869,635	620,606
Prepayments, calls, and maturities of held to maturity securities				7,190	6,170
Prepayments, calls, and maturities of other assets				17,793	29,136
Net cash received in acquisition				1,132	0
Net cash used in investing activities				(1,273,148)	(1,515,913)
CASH FLOWS FROM FINANCING ACTIVITIES
Net increase in deposits				1,794,891	934,091
Net increase (decrease) in short-term funding				(45,953)	689,254
Repayment of long-term funding				(1,500,026)	(155,058)
Proceeds from issuance of long-term funding				250,000	0
Purchase of common stock returned to authorized but unissued				(93,000)	(50,498)
Purchase of treasury stock				(5,070)	(112,245)
Proceeds from issuance of preferred stock				62,966	0
Purchase of preferred stock				(1,335)	(960)
Cash dividends on common stock				(45,599)	(43,299)
Cash dividends on preferred stock				(4,957)	(3,777)
Net cash provided by financing activities				411,917	1,257,508
Net decrease in cash and cash equivalents				(621,853)	(127,693)
Cash and cash equivalents at beginning of period				1,032,067	602,245	602,245
Cash and cash equivalents at end of period	410,214	474,552	410,214	410,214	474,552	1,032,067
Supplemental disclosures of cash flow information:
Cash paid for interest				59,751	46,026
Cash paid for income taxes				58,975	57,167
Loans and bank premises transferred to other real estate owned				5,782	17,125
Capitalized mortgage servicing rights				9,853	5,844	8,253
Unsettled trades to sell securities	139,286		139,286	139,286		$ 0
Acquisition:
Fair value of assets acquired, including cash and cash equivalents	4,590	0	4,590	4,590	0
Fair value ascribed to goodwill and intangible assets	51,791	0	51,791	51,791	0
Fair value of liabilities assumed	$ 12,851	$ 0	$ 12,851	12,851	0
Common stock issued in acquisition				$ 43,530	$ 0