Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Revenue from Contracts with Customers
Net interest income	$ 535,734	$ 573,402	$ 566,318
Not in scope of Topic 606	48,106	25,137	(5,838)
Total noninterest income	197,380	192,533	178,993
Total revenue	733,114	765,935	745,311
Retail Banking
Revenue from Contracts with Customers
Net interest income	393,466	413,029	420,165
Not in scope of Topic 606	16,264	8,844	8,917
Total noninterest income	98,026	95,413	89,669
Total revenue	491,492	508,442	509,834
Commercial Banking
Revenue from Contracts with Customers
Net interest income	133,301	141,227	140,333
Not in scope of Topic 606	19,945	7,368	(9,165)
Total noninterest income	78,202	73,635	80,904
Total revenue	211,503	214,862	221,237
Treasury and Other
Revenue from Contracts with Customers
Net interest income	8,967	19,146	5,820
Not in scope of Topic 606	11,897	8,925	(5,590)
Total noninterest income	21,152	23,485	8,420
Total revenue	30,119	42,631	14,240
Service charges on deposit accounts.
Revenue from Contracts with Customers
Revenue by type of service	28,169	33,778	32,036
Service charges on deposit accounts. | Retail Banking
Revenue from Contracts with Customers
Revenue by type of service	25,326	30,298	28,866
Service charges on deposit accounts. | Commercial Banking
Revenue from Contracts with Customers
Revenue by type of service	1,305	1,238	1,146
Service charges on deposit accounts. | Treasury and Other
Revenue from Contracts with Customers
Revenue by type of service	1,538	2,242	2,024
Credit and debit card fees
Revenue from Contracts with Customers
Revenue by type of service	53,372	64,846	85,298
Credit and debit card fees | Commercial Banking
Revenue from Contracts with Customers
Revenue by type of service	48,999	58,034	78,218
Credit and debit card fees | Treasury and Other
Revenue from Contracts with Customers
Revenue by type of service	4,373	6,812	7,080
Other service charges and fees.
Revenue from Contracts with Customers
Revenue by type of service	23,167	24,705	26,241
Other service charges and fees. | Retail Banking
Revenue from Contracts with Customers
Revenue by type of service	20,084	20,454	19,977
Other service charges and fees. | Commercial Banking
Revenue from Contracts with Customers
Revenue by type of service	1,550	2,096	4,089
Other service charges and fees. | Treasury and Other
Revenue from Contracts with Customers
Revenue by type of service	1,533	2,155	2,175
Trust and investment services income
Revenue from Contracts with Customers
Revenue by type of service	35,652	35,102	31,324
Trust and investment services income | Retail Banking
Revenue from Contracts with Customers
Revenue by type of service	35,652	35,102	31,324
Other
Revenue from Contracts with Customers
Revenue by type of service	8,914	8,965	9,932
Other | Retail Banking
Revenue from Contracts with Customers
Revenue by type of service	700	715	585
Other | Commercial Banking
Revenue from Contracts with Customers
Revenue by type of service	6,403	4,899	6,616
Other | Treasury and Other
Revenue from Contracts with Customers
Revenue by type of service	$ 1,811	$ 3,351	$ 2,731