Investment securities available for sale (Details Textual) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Schedule of Available-for-sale Securities [Line Items] | |||
| Purchase Of Rehabilitated Student Loans With Variable Interest Rates | $ 15,000,000 | ||
| Pledged Assets Separately Reported, Securities Pledged for Repurchase Agreements, at Fair Value | $ 1,050,000 | $ 5,968,000 | |
| Proceeds from Sale of Available-for-sale Securities, Debt | 22,000,000 | 8,000,000 | 22,000,000 |
| Available-for-sale Securities, Gross Realized Gain (Loss) | $ 162,000 | $ 6,000 | $ (210,000) |