Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Cash Flows from Operating Activities:
Net income	$ 106,552	$ 103,957
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for loan losses	9,571	(4,008)
Depreciation	8,382	8,043
Amortization of discounts and premiums, net	(2,044)	(1,216)
Amortization of core deposit intangibles		154
Net gain on sales of securities	466	(1,979)
Gain on trading securities activity	(172)
Net gain on sales of loans	(37)	(4,709)
Stock-based compensation	9,762	8,732
Deferred tax expense	3,175	23,693
Changes in operating assets and liabilities:
Decrease in other assets	18,868	61,391
Decrease in other liabilities	(5,960)	(26,138)
Purchases of securities held for trading	(110,000)
Proceeds from sales of securities held for trading	110,172
Origination of loans held for sale		(560,186)
Proceeds from sales of loans originated for sale		762,365
Net cash provided by operating activities	148,269	370,099
Cash Flows from Investing Activities:
Proceeds from repayment of securities held to maturity		85,024
Proceeds from repayment of securities available for sale	346,614	33
Proceeds from sales of securities available for sale		139,002
Purchase of securities held to maturity		(13,030)
Purchase of securities available for sale	(292,927)	(84,000)
Redemption of Federal Home Loan Bank stock	12,330	34,641
Purchases of Federal Home Loan Bank stock	(31,500)	(21,651)
Proceeds from bank-owned life insurance	7,785
Proceeds from sales of loans	31,528	214,596
Other changes in loans, net	(535,564)	(73,257)
Purchase of premises and equipment, net	(4,039)	(13,671)
Net cash (used in) provided by investing activities	(465,773)	267,687
Cash Flows from Financing Activities:
Net increase (decrease) in deposits	133,271	(161,357)
Net increase (decrease) in short-term borrowed funds		(460,000)
Proceeds from long-term borrowed funds	1,950,000
Repayments of long-term borrowed funds	(1,520,000)
Net proceeds from issuance of preferred stock		503,116
Cash dividends paid on common stock	(83,242)	(82,967)
Cash dividends paid on preferred stock	(8,207)
Payments relating to treasury shares received for restricted stock award tax payments	(1,715)	(10,132)
Net cash provided by (used in) financing activities	470,107	(211,340)
Net increase in cash and cash equivalents	152,603	426,446
Cash and cash equivalents at beginning of period	2,528,169	557,850
Cash and cash equivalents at end of period	2,680,772	984,296
Supplemental information:
Cash paid for interest	131,160	102,821
Cash paid for income taxes	5,236	1
Non-cash investing and financing activities:
Transfers to repossessed assets from loans	800	5,911
Transfer of loans from held for investment to held for sale	31,491	214,862
Shares issued for restricted stock awards	$ 8,566	$ 10,311