Loans and Allowance for Credit Losses - Activity in the Allowance for Loan Losses, by Portfolio Segment, for the Current Year (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	$ 68,244
Balance, end of period	238,050	$ 68,244
Loans, Excluding Acquired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	68,244	56,694	$ 42,086
Provision for credit loss expense	82,488	43,240	38,148
Charge-offs	(70,659)	(36,836)	(26,838)
Recoveries	6,600	5,146	3,298
Net charge-offs	(64,059)	(31,690)	(23,540)
Balance, end of period	238,050	68,244	56,694
Loans, Excluding Acquired Loans | Other Consumer and Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	2,169	2,419	3,596
Provision for credit loss expense	(6,093)	2,400	4,941
Charge-offs	(4,022)	(5,007)	(6,675)
Recoveries	1,465	2,357	557
Net charge-offs	(2,557)	(2,650)	(6,118)
Balance, end of period	5,617	2,169	2,419
Loans, Excluding Acquired Loans | Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	22,863	20,514	7,007
Provision for credit loss expense	42,017	24,434	21,176
Charge-offs	(48,736)	(23,352)	(8,414)
Recoveries	3,216	1,267	745
Net charge-offs	(45,520)	(22,085)	(7,669)
Balance, end of period	42,093	22,863	20,514
Loans, Excluding Acquired Loans | Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	39,161	29,838	27,699
Provision for credit loss expense	42,276	12,714	8,846
Charge-offs	(13,788)	(3,892)	(7,698)
Recoveries	905	501	991
Net charge-offs	(12,883)	(3,391)	(6,707)
Balance, end of period	182,868	39,161	29,838
Loans, Excluding Acquired Loans | Consumer | Credit Card
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	4,051	3,923	3,784
Provision for credit loss expense	4,288	3,692	3,185
Charge-offs	(4,113)	(4,585)	(4,051)
Recoveries	1,014	1,021	1,005
Net charge-offs	(3,099)	(3,564)	(3,046)
Balance, end of period	7,472	4,051	$ 3,923
Impact of ASU 2016-13 adoption | Loans, Excluding Acquired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	151,377
Balance, end 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
Balance, end 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
Balance, end 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
Balance, end of period		114,314
Impact of ASU 2016-13 adoption | Loans, Excluding Acquired Loans | Consumer | Credit Card
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	$ 2,232
Balance, end of period		$ 2,232