Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016	Dec. 31, 2015
Tax credit carryforwards
Interest and penalty expense recognized related to unrecognized tax benefits	$ 200	$ 200	$ 200
Reconciliation of the beginning and ending balance of unrecognized tax benefits
Balance at beginning of year	7,671	7,960
Increase (decrease) in unrecognized tax benefits as a result of tax positions taken during a prior period	76
Increase (decrease) in unrecognized tax benefits as a result of tax positions taken during a prior period		(78)
Decreases in unrecognized tax benefits related to settlements with tax authorities		(211)
Reductions to unrecognized tax benefits as a result of a lapse of the applicable statute of limitations	(903)
Balance at end of year	6,844	7,671	7,960
Recorded as other long-term liability				$ 1,462	$ 2,142
Recorded as a decrease in deferred tax assets and offsetting valuation allowance				5,382	5,529
Unrecognized tax benefits	$ 7,671	$ 7,960	$ 7,960	6,844	$ 7,671
Research and development and other tax credit carryforwards
Tax credit carryforwards
Tax credit carryforwards				$ 12,800