CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net income	$ 45,557	$ 147,423
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization and accretion, net	(11,590)	(22,452)
Provision for credit losses	150,842	7,534
Gain on sale of loans, net	(7,792)	(5,057)
Gain on investment securities, net	(3,383)	(9,901)
Equity based compensation	7,351	11,251
Depreciation and amortization	35,691	35,555
Deferred income taxes	(769)	10,813
Proceeds from sale of loans held for sale	369,807	209,854
Loans originated for sale, net of repayments	(17,681)	(51,024)
Other:
(Increase) decrease in other assets	(23,101)	31,897
Decrease in other liabilities	(224,093)	(128,097)
Net cash provided by operating activities	320,839	237,796
Net Cash Provided by (Used in) Investing Activities [Abstract]
Purchase of investment securities	(2,263,847)	(2,160,715)
Proceeds from repayments and calls of investment securities	587,139	647,214
Proceeds from sale of investment securities	547,337	1,626,250
Purchase of non-marketable equity securities	(128,562)	(196,137)
Proceeds from redemption of non-marketable equity securities	149,175	173,400
Purchases of loans	(1,085,437)	(894,235)
Loan originations, repayments and resolutions, net	68,012	(51,014)
Proceeds from sale of loans, net	11,604	9,560
Acquisition of operating lease equipment	(19,118)	(37,122)
Other investing activities	(10,663)	(24,950)
Net cash used in investing activities	(2,144,360)	(898,763)
Cash flows from financing activities:
Net increase in deposits	1,675,833	448,177
Net increase in federal funds purchased	0	(76,000)
Additions to Federal Home Loan Bank advances	3,762,336	2,456,000
Repayments of Federal Home Loan Bank advances	(3,596,310)	(1,921,000)
Proceeds from Issuance of Subordinated Long-term Debt	293,858	0
Dividends paid	(42,702)	(42,937)
Repurchase of common stock	(100,972)	(142,065)
Proceeds from Sale of Machinery and Equipment	0	8,986
Other financing activities	19,036	(448)
Net cash provided by financing activities	2,011,079	721,727
Net (decrease) increase in cash and cash equivalents	187,558	60,760
Cash and cash equivalents, beginning of period	214,673	382,073
Cash and cash equivalents, end of period	402,231	442,833
Supplemental Cash Flow Information [Abstract]
Interest paid	209,233	258,561
Income taxes (refunded) paid, net	4,883	(4,350)
Unsettled Sale of Loans	11,058
Supplemental schedule of non-cash investing and financing activities:
Transfers from loans to other real estate owned and other repossessed assets	4,161	2,817
Transfers from loans to loans held for sale	329,308	342,310
Transfer of Loans Held-for-sale to Portfolio Loans	9,055	0
Dividends declared, not paid	21,909	20,621
Unsettled sales of investment securities	177,546
Noncash or Part Noncash Acquisition, Investments Acquired	$ 2,758	$ 21,396