Income Taxes - Changes in Unrecognized Tax Benefits (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($)
Changes in unrecognized tax benefits [Roll Forward]
Balance at beginning of period	$ 1,734
Increases due to tax positions taken during the current year	303
Decreases due to tax positions taken during a prior year	(853)
Decreases due to the lapse of applicable statute of limitations during the current year	(79)
Balance at end of period	1,105
Accrued interest, net of federal benefit, at end of period	217
Unrecognized tax benefits that would impact the effective tax rate, if recognized, at end of period	$ 883