Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash Flows from Operating Activities:
Net income	$ 213,906	$ 219,212
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for (recovery of) loan losses	14,285	(10,269)
Depreciation	16,549	16,001
Amortization of discounts and premiums, net	(3,095)	(2,130)
Amortization of core deposit intangibles		184
Net gain on sales of securities		(28,915)
Gain on trading securities activity	(178)
Net gain on sales of loans	(178)	(10,501)
Stock-based compensation	18,714	18,195
Deferred tax expense	4,620	27,766
Changes in operating assets and liabilities:
Decrease in other assets	10,140	101,612
Increase in other liabilities	36,492	51,393
Purchases of securities held for trading	(113,615)
Proceeds from sales of securities held for trading	113,793
Origination of loans held for sale		(1,122,084)
Proceeds from sales of loans originated for sale	35,258	1,275,991
Net cash provided by operating activities	346,691	536,455
Cash Flows from Investing Activities:
Proceeds from repayment of securities held to maturity		175,375
Proceeds from repayment of securities available for sale	416,555	2,614
Proceeds from sales of securities held to maturity		547,925
Proceeds from sales of securities available for sale		139,009
Purchase of securities held to maturity		(13,030)
Purchase of securities available for sale	(1,116,898)	(84,000)
Redemption of Federal Home Loan Bank stock	51,139	65,161
Purchases of Federal Home Loan Bank stock	(100,395)	(63,294)
Proceeds from bank-owned life insurance	9,457
Proceeds from sales of loans	78,058	364,164
Other changes in loans, net	(1,149,413)	(89,365)
Purchase of premises and equipment, net	(7,619)	(22,648)
Net cash (used in) provided by investing activities	(1,819,116)	1,021,911
Cash Flows from Financing Activities:
Net increase in deposits	453,682	5,662
Net decrease in short-term borrowed funds		(460,000)
Proceeds from long-term borrowed funds	3,450,000
Repayments of long-term borrowed funds	(2,570,000)	(850,000)
Net proceeds from issuance of preferred stock		502,840
Cash dividends paid on common stock	(166,607)	(166,031)
Cash dividends paid on preferred stock	(16,414)	(8,207)
Payments relating to treasury shares received for restricted stock award tax payments	(2,008)	(10,634)
Net cash provided by (used in) financing activities	1,148,653	(986,370)
Net (decrease) increase in cash and cash equivalents	(323,772)	571,996
Cash and cash equivalents at beginning of period	2,528,169	557,850
Cash and cash equivalents at end of period	2,204,397	1,129,846
Supplemental information:
Cash paid for interest	280,653	214,315
Cash paid for income taxes	13,884	67,651
Non-cash investing and financing activities:
Transfers to repossessed assets from loans	2,461	9,558
Transfer of loans from held for investment to held for sale	77,880	1,843,765
Shares issued for restricted stock awards	$ 8,879	10,312
Securities transferred from held to maturity to available for sale		$ 3,040,305