Loans and Allowance for Credit Losses - Schedule of Allowance for Credit Losses and Amortized Cost Basis (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Allowance for loan losses:
Individually evaluated for impairment			$ 8,897
Collectively evaluated for impairment			45,527
Total allowance for loan losses	$ 106,380	$ 54,619	54,619	$ 55,559	$ 55,461
Loans and leases outstanding:
Individually evaluated for impairment			104,767
Total loans and leases outstanding	12,384,612	12,117,524	12,117,524
Financial Asset Acquired with Credit Deterioration
Allowance for loan losses:
Total allowance for loan losses			195
Loans and leases outstanding:
Collectively evaluated for impairment			11,978,895
Total loans and leases outstanding			33,862
Commercial
Allowance for loan losses:
Individually evaluated for impairment			7,891
Collectively evaluated for impairment			14,692
Total allowance for loan losses	31,125	21,359	22,585	20,406	21,742
Loans and leases outstanding:
Individually evaluated for impairment			41,479
Total loans and leases outstanding	2,844,465	2,815,154	2,890,296
Commercial | Financial Asset Acquired with Credit Deterioration
Allowance for loan losses:
Total allowance for loan losses			2
Loans and leases outstanding:
Collectively evaluated for impairment			2,843,536
Total loans and leases outstanding			5,281
Commercial real estate
Allowance for loan losses:
Individually evaluated for impairment			1,006
Collectively evaluated for impairment			20,582
Total allowance for loan losses	54,103	20,535	21,588	25,169	23,470
Loans and leases outstanding:
Individually evaluated for impairment			63,288
Total loans and leases outstanding	5,118,439	4,889,253	5,166,792
Commercial real estate | Financial Asset Acquired with Credit Deterioration
Allowance for loan losses:
Total allowance for loan losses			0
Loans and leases outstanding:
Collectively evaluated for impairment			5,084,737
Total loans and leases outstanding			18,767
Residential real estate
Allowance for loan losses:
Individually evaluated for impairment			0
Collectively evaluated for impairment			2,299
Total allowance for loan losses	9,637	2,299	2,299	2,302	2,277
Loans and leases outstanding:
Individually evaluated for impairment			0
Total loans and leases outstanding	$ 2,327,851	$ 2,334,289	2,334,289
Residential real estate | Financial Asset Acquired with Credit Deterioration
Allowance for loan losses:
Total allowance for loan losses			0
Loans and leases outstanding:
Collectively evaluated for impairment			2,326,907
Total loans and leases outstanding			7,382
Consumer
Allowance for loan losses:
Individually evaluated for impairment			0
Collectively evaluated for impairment			7,954
Total allowance for loan losses			8,147	$ 7,682	$ 7,972
Loans and leases outstanding:
Individually evaluated for impairment			0
Total loans and leases outstanding			1,726,147
Consumer | Financial Asset Acquired with Credit Deterioration
Allowance for loan losses:
Total allowance for loan losses			193
Loans and leases outstanding:
Collectively evaluated for impairment			1,723,715
Total loans and leases outstanding			$ 2,432