CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net income	$ 112,116	$ 223,642
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization and accretion, net	(20,102)	(30,550)
Provision for credit losses	180,074	9,373
Gain on sale of loans, net	(10,745)	(10,220)
Gain on investment securities, net	(10,564)	(13,736)
Equity based compensation	12,286	16,967
Depreciation and amortization	54,377	53,105
Deferred income taxes	(27,304)	22,278
Gain (Loss) on Extinguishment of Debt		3,796
Proceeds from sale of loans held for sale	498,431	317,027
Loans originated for sale, net of repayments	(21,780)	(68,665)
Other:
Decrease in other assets	2,509	20,288
Decrease in other liabilities	(134,363)	(131,066)
Net cash provided by operating activities	634,935	412,239
Net Cash Provided by (Used in) Investing Activities [Abstract]
Purchase of investment securities	(3,356,639)	(3,176,833)
Proceeds from repayments and calls of investment securities	912,403	1,057,043
Proceeds from sale of investment securities	930,757	2,297,121
Purchase of non-marketable equity securities	(134,938)	(319,387)
Proceeds from redemption of non-marketable equity securities	179,988	313,650
Purchases of loans	(2,082,695)	(1,636,932)
Loan originations, repayments and resolutions, net	1,000,352	332,246
Proceeds from sale of loans, net	11,604	205,869
Acquisition of operating lease equipment	(19,597)	(38,312)
Other investing activities	(12,328)	(27,005)
Net cash used in investing activities	(2,571,093)	(992,540)
Cash flows from financing activities:
Net increase in deposits	2,202,619	482,205
Net increase in federal funds purchased	80,000	0
Additions to Federal Home Loan Bank advances	4,281,960	3,962,000
Repayments of Federal Home Loan Bank advances	(4,647,310)	(3,827,000)
Proceeds from Issuance of Subordinated Long-term Debt	293,858	0
Dividends paid	(64,611)	(63,558)
Repurchase of common stock	(100,972)	(150,000)
Other financing activities	45,717	24,809
Net cash provided by financing activities	2,091,261	428,456
Net (decrease) increase in cash and cash equivalents	155,103	(151,845)
Cash and cash equivalents, beginning of period	214,673	382,073
Cash and cash equivalents, end of period	369,776	230,228
Supplemental Cash Flow Information [Abstract]
Interest paid	268,970	391,691
Income taxes (refunded) paid, net	5,944	(264)
Supplemental schedule of non-cash investing and financing activities:
Transfers from loans to other real estate owned and other repossessed assets	4,170	3,211
Transfers from loans to loans held for sale	451,864	439,525
Transfer of Loans Held-for-sale to Portfolio Loans	9,055	19,716
Dividends declared, not paid	21,910	20,524
Noncash or Part Noncash Acquisition, Investments Acquired	$ 10,339	$ 88,331