Fair Value Measurements - Recorded Amounts of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	$ 542,703	$ 565,135
U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	300	300
Agency Mortgage-backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	498,886	536,148
Beneficial interest – FHLMC securitizations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	43,517	12,674
FNMA and FHLB Agency Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale		16,013
Fair Value on Recurring Basis
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	542,703	565,135
Fair Value on Recurring Basis | U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	300	300
Fair Value on Recurring Basis | Agency Mortgage-backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	498,886	536,148
Fair Value on Recurring Basis | Beneficial interest – FHLMC securitizations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	43,517	12,674
Fair Value on Recurring Basis | FNMA and FHLB Agency Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale		16,013
Fair Value Measurement Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	300	300
Fair Value Measurement Level 1 | Fair Value on Recurring Basis
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	300	300
Fair Value Measurement Level 1 | Fair Value on Recurring Basis | U.S. Treasury Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	300	300
Fair Value Measurement Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	498,886	552,161
Fair Value Measurement Level 2 | Fair Value on Recurring Basis
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	498,886	552,161
Fair Value Measurement Level 2 | Fair Value on Recurring Basis | Agency Mortgage-backed Securities
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	498,886	536,148
Fair Value Measurement Level 2 | Fair Value on Recurring Basis | FNMA and FHLB Agency Notes
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale		16,013
Fair Value Measurement Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	43,517	12,674
Fair Value Measurement Level 3 | Fair Value on Recurring Basis
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	43,517	12,674
Fair Value Measurement Level 3 | Fair Value on Recurring Basis | Beneficial interest – FHLMC securitizations
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Investment securities available for sale	$ 43,517	$ 12,674