Balance Sheet Components - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 679,617	$ 554,339
Other comprehensive income before reclassifications	769	2,873
Amounts reclassified from other comprehensive income (loss), net of tax	(417)	(199)
Net current-period other comprehensive income (loss), net of tax	352	2,674
Unrealized gains (losses) on interest rate swap contracts	(317)	202
Ending balance	730,485	574,502
Foreign currency translation adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(11,274)	(6,954)
Other comprehensive income before reclassifications	669	2,472
Amounts reclassified from other comprehensive income (loss), net of tax	0	0
Net current-period other comprehensive income (loss), net of tax	669	2,472
Ending balance	(10,605)	(4,482)
Unrealized gain (loss) on interest rate swap hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	420	841
Other comprehensive income before reclassifications	100	401
Amounts reclassified from other comprehensive income (loss), net of tax	(417)	(199)
Net current-period other comprehensive income (loss), net of tax	(317)	202
Ending balance	103	1,043
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(10,854)	(6,113)
Ending balance	$ (10,502)	$ (3,439)

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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Amount before tax and reclassification adjustments of other comprehensive income (loss) attributable to parent.

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Amount before tax of other comprehensive income (loss) attributable to parent entity.

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Amount after tax of increase (decrease) in accumulated gain (loss) from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's increase (decrease) in deferred hedging gain (loss).

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