Loans and Allowance for Credit Losses - Schedule of Types of Collateral (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Jan. 01, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 12,384,612	$ 12,117,524	$ 12,117,524
Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	77,746
Blanket Lien
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	24,939
Investment Securities/Cash
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	11,475
Auto
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3,792
Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,701
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,844,465	2,815,154	2,890,296
Commercial | Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	6,802
Commercial | Blanket Lien
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	23,175
Commercial | Investment Securities/Cash
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	8,209
Commercial | Auto
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	396
Commercial | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,522
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	5,118,439	4,889,253	5,166,792
Commercial real estate | Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	40,361
Commercial real estate | Blanket Lien
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	150
Commercial real estate | Investment Securities/Cash
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3,199
Commercial real estate | Auto
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Commercial real estate | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	179
BBCC
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	367,139	352,681
BBCC | Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,930
BBCC | Blanket Lien
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,614
BBCC | Investment Securities/Cash
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	59
BBCC | Auto
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	246
BBCC | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Residential real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,327,851	2,334,289	2,334,289
Residential real estate | Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	23,567		559,021
Residential real estate | Blanket Lien
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Residential real estate | Investment Securities/Cash
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Residential real estate | Auto
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0		1,017,287
Residential real estate | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0		$ 149,839
Indirect
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	953,136	935,584
Indirect | Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Indirect | Blanket Lien
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Indirect | Investment Securities/Cash
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Indirect | Auto
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,885
Indirect | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Direct
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	211,793	228,524
Direct | Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	863
Direct | Blanket Lien
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Direct | Investment Securities/Cash
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	8
Direct | Auto
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	265
Direct | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Home equity
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	561,789	$ 562,039
Home equity | Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4,223
Home equity | Blanket Lien
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Home equity | Investment Securities/Cash
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Home equity | Auto
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Home equity | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 0