Allowance for Credit Losses - Disaggregation of ACL by Impairment Methodology (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Allowance for loan and lease losses:
Individually evaluated for impairment		$ 203	$ 536
Collectively evaluated for impairment		130,327	141,182
Total allowance for loan and lease losses	$ 208,454	130,530	141,718	$ 137,253
Loans and leases:
Individually evaluated for impairment		20,638	30,576
Collectively evaluated for impairment		13,191,012	13,045,615
Total loans and leases	13,279,097	13,211,650	13,076,191
Commercial and Industrial
Allowance for loan and lease losses:
Individually evaluated for impairment		46	108
Collectively evaluated for impairment		28,929	34,393
Total allowance for loan and lease losses	24,711	28,975	34,501	34,006
Loans and leases:
Individually evaluated for impairment		4,951	8,719
Collectively evaluated for impairment		2,738,291	3,200,041
Total loans and leases	3,019,507	2,743,242	3,208,760
Commercial real estate
Allowance for loan and lease losses:
Individually evaluated for impairment		27	32
Collectively evaluated for impairment		22,298	19,693
Total allowance for loan and lease losses	58,123	22,325	19,725	18,044
Loans and leases:
Individually evaluated for impairment		723	5,743
Collectively evaluated for impairment		3,463,230	2,985,040
Total loans and leases	3,392,676	3,463,953	2,990,783
Construction
Allowance for loan and lease losses:
Collectively evaluated for impairment		4,844	5,813
Total allowance for loan and lease losses	10,039	4,844	5,813	6,817
Loans and leases:
Collectively evaluated for impairment		519,241	626,757
Total loans and leases	735,819	519,241	626,757
Lease financing
Allowance for loan and lease losses:
Collectively evaluated for impairment		424	432
Total allowance for loan and lease losses	3,298	424	432	611
Loans and leases:
Collectively evaluated for impairment		202,483	147,769
Total loans and leases	245,411	202,483	147,769
Residential
Allowance for loan and lease losses:
Individually evaluated for impairment		130	396
Collectively evaluated for impairment		39,049	44,510
Total allowance for loan and lease losses		39,179	44,906	42,852
Loans and leases:
Individually evaluated for impairment		14,964	16,114
Collectively evaluated for impairment		4,647,211	4,423,504
Total loans and leases	3,690,218	4,662,175	4,439,618
Consumer
Allowance for loan and lease losses:
Collectively evaluated for impairment		34,644	35,813
Total allowance for loan and lease losses	64,659	34,644	35,813	31,249
Loans and leases:
Collectively evaluated for impairment		1,620,556	1,662,504
Total loans and leases	$ 1,353,842	1,620,556	1,662,504
Unallocated
Allowance for loan and lease losses:
Collectively evaluated for impairment		139	528
Total allowance for loan and lease losses		$ 139	$ 528	$ 3,674