Income Taxes - Reconciliation of Beginning and Ending Amounts of Gross Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns
Unrecognized tax benefits at beginning of year	$ 1,485	$ 2,155	$ 4,009
Additions as a result of a tax position taken during the current period	15	830	675
Reductions relating to settlement with taxing authorities	(88)	(1,500)	(2,529)
Unrecognized tax benefits at end of year	$ 1,412	$ 1,485	$ 2,155