Loans Held for Investment (LHFI) and Allowance for Loan Losses, LHFI - Additional Information (Details 1)	3 Months Ended
	Mar. 31, 2017 USD ($) Region	Mar. 31, 2016 USD ($)	Jan. 01, 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
Carrying amounts of nonaccrual LHFI considered for impairment analysis	$ 61,300,000			$ 49,200,000
Nonaccrual	61,307,000			49,234,000
Minimum loan amount for loan to be specifically reviewed for impairment and deemed impaired			$ 500,000
Amount held by company of foreclosure or in substance repossession of consumer mortgage LHFI classified as TDRs	234,000			269,000
TDRs Classified as Consumer mortgage LHFI in the process of formal disclosure	107,000			101,000
LHFI Classified as TDRs	12,400,000	$ 9,200,000
LHFI classified as TDRs from credits with interest only payments	9,500,000	5,700,000
Financing receivable, related allowance	382,000	1,700,000
Financing receivable, related charge-offs	0	0
Troubled Debt Restructurings [Member]
Financing Receivable Impaired [Line Items]
Nonaccrual	$ 12,399,000	$ 6,945,000		$ 14,400,000