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
	Mar. 31, 2021	Mar. 31, 2020
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	$ 238,050
Provision for credit loss expense	1,445	$ 23,134
Balance, end of period	235,116
Loans, Excluding Acquired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	238,050	68,244
Provision for credit loss expense	0	26,197
Charge-offs	(4,251)	(3,739)
Recoveries	1,317	1,116
Net charge-offs	(2,934)	(2,623)
Balance, end of period	235,116	243,195
Loans, Excluding Acquired Loans | Other Consumer and Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	5,617	2,169
Provision for credit loss expense	(2,715)	4,698
Charge-offs	(731)	(1,379)
Recoveries	314	443
Net charge-offs	(417)	(936)
Balance, end of period	2,485	18,029
Loans, Excluding Acquired Loans | Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	42,093	22,863
Provision for credit loss expense	(6,940)	30,907
Charge-offs	(830)	(523)
Recoveries	310	347
Net charge-offs	(520)	(176)
Balance, end of period	34,633	76,327
Loans, Excluding Acquired Loans | Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	182,868	39,161
Provision for credit loss expense	14,242	(12,158)
Charge-offs	(1,687)	(396)
Recoveries	403	101
Net charge-offs	(1,284)	(295)
Balance, end of period	195,826	141,022
Loans, Excluding Acquired Loans | Consumer | Credit cards
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period	7,472	4,051
Provision for credit loss expense	(4,587)	2,750
Charge-offs	(1,003)	(1,441)
Recoveries	290	225
Net charge-offs	(713)	(1,216)
Balance, end of period	$ 2,172	7,817
Cumulative Effect, Period of Adoption, Adjustment | Loans, Excluding Acquired Loans
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period		151,377
Cumulative Effect, Period of Adoption, Adjustment | Loans, Excluding Acquired Loans | Other Consumer and Other
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period		12,098
Cumulative Effect, Period of Adoption, Adjustment | Loans, Excluding Acquired Loans | Commercial
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period		22,733
Cumulative Effect, Period of Adoption, Adjustment | Loans, Excluding Acquired Loans | Real Estate
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period		114,314
Cumulative Effect, Period of Adoption, Adjustment | Loans, Excluding Acquired Loans | Consumer | Credit cards
Allowance for Loan and Lease Losses [Roll Forward]
Balance, beginning of period		$ 2,232