Income Taxes - Change in Gross Unrecognized Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Summary of gross unrecognized income tax benefits
Unrecognized tax benefits at beginning of period	$ 17,513	$ 21,347	$ 27,545
Gross increases – tax positions in prior period	0	0	44
Gross increases – tax positions in current period	884	8,384	0
Gross decreases – tax positions in prior period	(298)	(7,597)	(1,724)
Lapse of Statute of Limitations	(939)	(4,621)	(4,518)
Unrecognized tax benefits at end of period	$ 17,160	$ 17,513	$ 21,347