| Amount of unrealized loss on securities classified as available-for-sale. | en-US | http://www.xbrl.org/2003/role/documentation | http://www.xbrl.org/2003/role/link |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss (Deprecated 2018-01-31) | en-US | http://www.xbrl.org/2003/role/label | http://www.xbrl.org/2003/role/link |
| Available-for-sale Securities, Continuous Unrealized Loss Position, Aggregate Loss, Total (Deprecated 2018-01-31) | en-US | http://www.xbrl.org/2003/role/totalLabel | http://www.xbrl.org/2003/role/link |