Loans and Allowance for Losses and Concentrations of Credit Risk - Troubled Debt Restructurings (Details)	3 Months Ended		6 Months Ended
	Jun. 30, 2016 USD ($) defaulted_loan	Jun. 30, 2015 USD ($) defaulted_loan	Jun. 30, 2016 USD ($) defaulted_loan	Jun. 30, 2015 USD ($) defaulted_loan
Receivables [Abstract]
Certain Loans Acquired In Transfer Not Accounted For As Debt Securities, Number Defaulted | defaulted_loan	0	1	5	2
Payments to Acquire Other Loans and Leases Held-for-investment	$ 0	$ 1,324,000	$ 1,415,000	$ 1,981,000
Financing Receivable, Modifications, Pre-Modification Recorded Investment	0	1,100,000		$ 1,100,000
Financing Receivable, Modifications, Post-Modification Recorded Investment	$ 0	$ 1,100,000
Financing Receivable, Modifications, Subsequent Default, Number of Contracts	0	0
Financing Receivable, Modifications, Subsequent Default, Recorded Investment	$ 0	$ 0
Financing Receivable, Modifications, Subsequent Default, Determination of Allowance for Credit Losses	0	0