v3.8.0.1
Fair Value - Recorded Amounts of Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($)
$ in Thousands
Mar. 31, 2018
Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale $ 513,067 $ 519,364
Investment in equity securities 400  
U.S. Treasury Securities    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale 493 493
Agency Mortgage-backed Securities    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale 438,868 464,019
Beneficial interest - FHLMC securitization    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale 34,606 19,000
Fair Value on Recurring Basis    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale   519,364
Investment in equity securities 400  
Investment securities available for sale 513,467  
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 493 493
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 438,868 464,019
Fair Value on Recurring Basis | Corporate Bonds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale 39,100 19,000
Fair Value on Recurring Basis | Beneficial interest - FHLMC securitization    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale 34,606 35,852
Fair Value Measurement Level 1    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale 493 493
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   493
Investment in equity securities 400  
Investment securities available for sale 893  
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 493 493
Fair Value Measurement Level 2    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale 477,968 483,019
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   483,019
Investment securities available for sale 477,968  
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 438,868 464,019
Fair Value Measurement Level 2 | Fair Value on Recurring Basis | Corporate Bonds    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale 39,100 19,000
Fair Value Measurement Level 3    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale 34,606 35,852
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   35,852
Investment securities available for sale 34,606  
Fair Value Measurement Level 3 | Fair Value on Recurring Basis | Beneficial interest - FHLMC securitization    
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]    
Investment securities available for sale $ 34,606 $ 35,852