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		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period			$ 68,244
Provision for credit loss expense	$ 26,915	$ 7,079	53,049	$ 16,364
Balance, end of period	231,643		231,643
Loans, Excluding Acquired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	243,195	60,555	68,244	56,694
Provision for credit loss expense	26,678	7,079	52,875	16,364
Charge-offs	(39,156)	(5,182)	(42,895)	(11,446)
Recoveries	926	1,727	2,042	2,567
Net charge-offs	(38,230)	(3,455)	(40,853)	(8,879)
Balance, end of period	231,643	64,179	231,643	64,179
Loans, Excluding Acquired Loans | Other Consumer and Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	18,029	2,372	2,169	2,419
Provision for credit loss expense	(5,685)	642	(987)	1,848
Charge-offs	(592)	(964)	(1,971)	(2,517)
Recoveries	303	331	746	631
Net charge-offs	(289)	(633)	(1,225)	(1,886)
Balance, end of period	12,055	2,381	12,055	2,381
Loans, Excluding Acquired Loans | Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	76,327	19,394	22,863	20,514
Provision for credit loss expense	18,400	2,956	49,307	4,830
Charge-offs	(35,687)	(1,963)	(36,210)	(5,115)
Recoveries	98	967	445	1,125
Net charge-offs	(35,589)	(996)	(35,765)	(3,990)
Balance, end of period	59,138	21,354	59,138	21,354
Loans, Excluding Acquired Loans | Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	141,022	34,870	39,161	29,838
Provision for credit loss expense	10,020	2,681	(2,138)	7,988
Charge-offs	(1,824)	(1,216)	(2,220)	(1,633)
Recoveries	253	158	354	300
Net charge-offs	(1,571)	(1,058)	(1,866)	(1,333)
Balance, end of period	149,471	36,493	149,471	36,493
Loans, Excluding Acquired Loans | Consumer | Credit cards
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	7,817	3,919	4,051	3,923
Provision for credit loss expense	3,943	800	6,693	1,698
Charge-offs	(1,053)	(1,039)	(2,494)	(2,181)
Recoveries	272	271	497	511
Net charge-offs	(781)	(768)	(1,997)	(1,670)
Balance, end of period	$ 10,979	$ 3,951	10,979	$ 3,951
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