Loans and Allowance for Credit Losses - Activity in the Allowance for Loan Losses, by Portfolio Segment, for the Current Year (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period			$ 68,244
Provision for credit loss expense	$ 22,981	$ 21,973	68,030	$ 38,337
Balance, end of period	248,251		248,251
Loans, Excluding Acquired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	231,643	64,179	68,244	56,694
Provision for credit loss expense	22,313	21,973	75,190	38,337
Charge-offs	(7,403)	(21,327)	(50,298)	(32,773)
Recoveries	1,698	1,765	3,738	4,332
Net charge-offs	(5,705)	(19,562)	(46,560)	(28,441)
Balance, end of period	248,251	66,590	248,251	66,590
Loans, Excluding Acquired Loans | Other Consumer and Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	12,055	2,381	2,169	2,419
Provision for credit loss expense	(2,844)	(528)	(3,829)	1,320
Charge-offs	(1,091)	(1,065)	(3,062)	(3,582)
Recoveries	366	1,422	1,110	2,053
Net charge-offs	(725)	357	(1,952)	(1,529)
Balance, end of period	8,486	2,210	8,486	2,210
Loans, Excluding Acquired Loans | Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	59,138	21,354	22,863	20,514
Provision for credit loss expense	(6,499)	19,150	42,808	23,980
Charge-offs	(4,327)	(17,778)	(40,537)	(22,893)
Recoveries	936	65	1,381	1,190
Net charge-offs	(3,391)	(17,713)	(39,156)	(21,703)
Balance, end of period	49,248	22,791	49,248	22,791
Loans, Excluding Acquired Loans | Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	149,471	36,493	39,161	29,838
Provision for credit loss expense	33,479	2,405	31,341	10,393
Charge-offs	(1,153)	(1,367)	(3,373)	(3,000)
Recoveries	120	55	474	355
Net charge-offs	(1,033)	(1,312)	(2,899)	(2,645)
Balance, end of period	181,917	37,586	181,917	37,586
Loans, Excluding Acquired Loans | Consumer | Credit cards
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	10,979	3,951	4,051	3,923
Provision for credit loss expense	(1,823)	946	4,870	2,644
Charge-offs	(832)	(1,117)	(3,326)	(3,298)
Recoveries	276	223	773	734
Net charge-offs	(556)	(894)	(2,553)	(2,564)
Balance, end of period	$ 8,600	$ 4,003	8,600	$ 4,003
Impact of ASU 2016-13 adoption | Loans, Excluding Acquired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period			151,377
Impact of ASU 2016-13 adoption | Loans, Excluding Acquired Loans | Other Consumer and Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period			12,098
Impact of ASU 2016-13 adoption | Loans, Excluding Acquired Loans | Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period			22,733
Impact of ASU 2016-13 adoption | Loans, Excluding Acquired Loans | Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period			114,314
Impact of ASU 2016-13 adoption | Loans, Excluding Acquired Loans | Consumer | Credit cards
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period			$ 2,232