Subordinated Debentures - Activities for our subordinated debentures (Details) - Subordinated Debentures - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Average balance outstanding	$ 81,466	$ 69,347
Maximum amount outstanding at any month-end during the year	105,123	69,383
Balance outstanding at end of year	$ 105,123	$ 69,383
Weighted average interest rate during the year	5.80%	5.54%