CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Cash flows from operating activities:
Net income	$ 147,423	$ 175,135
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization and accretion, net	(22,452)	(69,157)
Provision for loan losses	7,534	12,142
Income from resolution of covered assets, net	0	(7,555)
Net loss on FDIC indemnification	0	5,015
Gain on sale of loans, net	(5,057)	(4,269)
Gain on investment securities, net	(9,901)	(2,506)
Equity based compensation	11,251	12,272
Depreciation and amortization	35,555	31,391
Deferred income taxes	10,813	24,074
Proceeds from sale of loans held for sale	209,854	86,118
Loans originated for sale, net of repayments	(51,024)	(73,633)
Other:
Decrease in other assets	31,897	15,625
Increase (decrease) in other liabilities	(128,097)	25,242
Net cash provided by operating activities	237,796	229,894
Net Cash Provided by (Used in) Investing Activities [Abstract]
Purchase of investment securities	(2,160,715)	(1,730,173)
Proceeds from repayments and calls of investment securities	647,214	691,220
Proceeds from sale of investment securities	1,626,250	836,317
Purchase of non-marketable equity securities	(196,137)	(166,813)
Proceeds from redemption of non-marketable equity securities	173,400	154,063
Purchases of loans	(894,235)	(604,278)
Loan originations, repayments and resolutions, net	(51,014)	152,848
Proceeds from sale of loans, net	9,560	115,560
Proceeds from sale of equipment under operating lease	8,986	49,892
Acquisition of equipment under operating lease	(37,122)	(56,132)
Other investing activities	(24,950)	(16,404)
Net cash used in investing activities	(898,763)	(573,900)
Cash flows from financing activities:
Net increase in deposits	448,177	299,471
Net decrease in federal funds purchased	(76,000)	0
Additions to Federal Home Loan Bank advances	2,456,000	2,201,000
Repayments of Federal Home Loan Bank advances	(1,921,000)	(1,901,000)
Dividends paid	(42,937)	(45,996)
Repurchase of common stock	(142,065)	(54,399)
Other financing activities	(448)	29,604
Net cash provided by financing activities	721,727	528,680
Net increase in cash and cash equivalents	60,760	184,674
Cash and cash equivalents, beginning of period	382,073	194,582
Cash and cash equivalents, end of period	442,833	379,256
Supplemental Cash Flow Information [Abstract]
Interest paid	258,561	171,379
Income taxes (refunded) paid, net	(4,350)	18,677
Supplemental schedule of non-cash investing and financing activities:
Transfers from loans to other real estate owned and other repossessed assets	2,817	7,574
Transfers from loans to loans held for sale	342,310	22,094
Dividends declared, not paid	20,621	22,916
Noncash or Part Noncash Acquisition, Investments Acquired	$ 21,396	$ 272,500