Loans and Allowance for Credit Losses - Schedule of Types of Collateral (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	$ 13,615,701	$ 12,117,524	$ 12,117,524
Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	78,547
Blanket Lien
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	23,690
Investment Securities/Cash
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	10,872
Auto
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3,736
Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,267
Commercial
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4,307,505	2,815,154	2,890,296
Commercial | Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	9,143
Commercial | Blanket Lien
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	19,503
Commercial | Investment Securities/Cash
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	7,628
Commercial | Auto
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	456
Commercial | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,107
Commercial real estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	5,403,316	4,889,253	5,166,792
Commercial real estate | Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	38,065
Commercial real estate | Blanket Lien
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	2,251
Commercial real estate | Investment Securities/Cash
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	3,156
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	160
BBCC
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans		352,681
BBCC | Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,836
BBCC | Blanket Lien
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	1,936
BBCC | Investment Securities/Cash
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	80
BBCC | Auto
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	190
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	2,229,298	2,334,289	2,334,289
Residential real estate | Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	24,315		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	933,723	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	2,835
Indirect | Other
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	0
Direct
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	194,573	228,524
Direct | Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	862
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	255
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	547,286	$ 562,039
Home equity | Real Estate
Financing Receivable, Allowance for Credit Losses [Line Items]
Total loans	4,326
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