Balance Sheet Components - Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' Equity, Beginning of period	$ 554,341	$ 458,836	$ 420,464
Other comprehensive income (loss) before reclassifications	(3,543)	4,219
Amounts reclassified from other comprehensive income (loss)	(1,198)	(813)
Other comprehensive gain (loss)	(4,741)	3,406	(6,789)
Stockholders' Equity, End of period	679,617	554,341	458,836
Foreign currency translation adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' Equity, Beginning of period	(6,954)	(10,764)
Other comprehensive income (loss) before reclassifications	(4,320)	3,810
Amounts reclassified from other comprehensive income (loss)	0	0
Other comprehensive gain (loss)	(4,320)	3,810
Stockholders' Equity, End of period	(11,274)	(6,954)	(10,764)
Unrealized gain (loss) on interest rate swap hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' Equity, Beginning of period	841	1,245
Other comprehensive income (loss) before reclassifications	777	409
Amounts reclassified from other comprehensive income (loss)	(1,198)	(813)
Other comprehensive gain (loss)	(421)	(404)
Stockholders' Equity, End of period	420	841	1,245
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Stockholders' Equity, Beginning of period	(6,113)	(9,519)	(2,730)
Other comprehensive gain (loss)	(4,741)	3,406	(6,789)
Stockholders' Equity, End of period	$ (10,854)	$ (6,113)	$ (9,519)