Deposit Accounts - The aggregate annual maturities of certificates of deposit accounts (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Balance
Within 3 months	$ 147,508
4 to 6 months	137,620
7 to 12 months	191,814
13 to 24 months	87,050
25 to 36 months	6,533
37 to 60 months	3,370
Over 60 months	664
Total certificates of deposit accounts	$ 574,559	$ 520,975
Weighted Average Interest Rate
Within 3 months (as a percent)	0.66%
4 to 6 months (as a percent)	0.74%
7 to 12 months (as a percent)	0.77%
13 to 24 months (as a percent)	0.92%
25 to 36 months (as a percent)	0.87%
37 to 60 months (as a percent)	1.29%
Over 60 months (as a percent)	0.90%
Total certificates of deposit accounts (as a percent)	0.76%	0.80%