Revenue from Contracts with Customers - Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from Contracts with Customers
Net interest income	$ 134,002	$ 143,081	$ 400,507	$ 433,783
Not in scope of Topic 606	11,307	9,334	34,082	23,293
Total noninterest income	48,898	49,980	143,782	145,825
Total revenue	182,900	193,061	544,289	579,608
Retail Banking
Revenue from Contracts with Customers
Net interest income	102,803	104,977	288,832	319,912
Not in scope of Topic 606	4,493	2,185	11,534	6,887
Total noninterest income	24,649	23,948	73,197	71,192
Total revenue	127,452	128,925	362,029	391,104
Commercial Banking
Revenue from Contracts with Customers
Net interest income	32,757	35,911	100,265	105,567
Not in scope of Topic 606	1,434	1,488	10,355	5,533
Total noninterest income	16,679	17,447	52,530	54,560
Total revenue	49,436	53,358	152,795	160,127
Treasury and Other
Revenue from Contracts with Customers
Net interest income	(1,558)	2,193	11,410	8,304
Not in scope of Topic 606	5,380	5,661	12,193	10,873
Total noninterest income	7,570	8,585	18,055	20,073
Total revenue	6,012	10,778	29,465	28,377
Service charges on deposit accounts.
Revenue from Contracts with Customers
Revenue by type of service	6,523	8,554	21,400	24,737
Service charges on deposit accounts. | Retail Banking
Revenue from Contracts with Customers
Revenue by type of service	5,734	7,772	19,290	22,136
Service charges on deposit accounts. | Commercial Banking
Revenue from Contracts with Customers
Revenue by type of service	332	304	1,009	924
Service charges on deposit accounts. | Treasury and Other
Revenue from Contracts with Customers
Revenue by type of service	457	478	1,101	1,677
Credit and debit card fees
Revenue from Contracts with Customers
Revenue by type of service	13,495	16,341	38,378	48,699
Credit and debit card fees | Commercial Banking
Revenue from Contracts with Customers
Revenue by type of service	12,259	14,623	35,268	43,564
Credit and debit card fees | Treasury and Other
Revenue from Contracts with Customers
Revenue by type of service	1,236	1,718	3,110	5,135
Other service charges and fees.
Revenue from Contracts with Customers
Revenue by type of service	6,324	5,998	17,271	18,631
Other service charges and fees. | Retail Banking
Revenue from Contracts with Customers
Revenue by type of service	5,433	5,155	14,887	15,429
Other service charges and fees. | Commercial Banking
Revenue from Contracts with Customers
Revenue by type of service	570	306	1,209	1,543
Other service charges and fees. | Treasury and Other
Revenue from Contracts with Customers
Revenue by type of service	321	537	1,175	1,659
Trust and investment services income
Revenue from Contracts with Customers
Revenue by type of service	8,664	8,698	26,919	26,247
Trust and investment services income | Retail Banking
Revenue from Contracts with Customers
Revenue by type of service	8,664	8,698	26,919	26,247
Other
Revenue from Contracts with Customers
Revenue by type of service	2,585	1,055	5,732	4,218
Other | Retail Banking
Revenue from Contracts with Customers
Revenue by type of service	325	138	567	493
Other | Commercial Banking
Revenue from Contracts with Customers
Revenue by type of service	2,084	726	4,689	2,996
Other | Treasury and Other
Revenue from Contracts with Customers
Revenue by type of service	$ 176	$ 191	$ 476	$ 729