LHFI and Allowance for Loan Losses, LHFI - Additional Information (Details 1) $ in Thousands	12 Months Ended
	Dec. 31, 2018 USD ($) Region	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Financing Receivable Impaired [Line Items]
Maximum concentration of loan as a percentage of total LHFI	10.00%
Key market regions | Region	5
Loans and Leases Receivable, Related Parties	$ 49,000	$ 59,900
New loan advances to related party	440,500
Loan repayment by related party	451,400
Loan increase (decreases) from changes in executive officers and directors	0
Carrying amounts of nonaccrual LHFI considered for impairment analysis	61,600	67,600
Nonaccrual	61,624	67,575
Minimum loan amount for loan to be specifically reviewed for impairment and deemed impaired	500
LHFI Classified as TDRs	28,200	23,900	$ 14,500
LHFI classified as TDRs from credits with interest only payments	23,800	20,500	9,800
Unused Commitments on TDRs	4,400
Financing receivable, related allowance	2,300	458	2,200
Financing receivable, related charge-offs	18,400	127	1,000
Troubled Debt Restructurings [Member]
Financing Receivable Impaired [Line Items]
Nonaccrual	$ 16,706	$ 23,211	$ 14,427