Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 24,779	$ 16,762	$ 55,157	$ 36,196
Other comprehensive income (loss):
Foreign currency translation adjustment	82	(11)	222	(119)
Tax benefit (provision)	(15)	7	(54)	43
Comprehensive income	$ 24,846	$ 16,758	$ 55,325	$ 36,120

Amount after tax of increase (decrease) in equity from transactions and other events and circumstances from net income and other comprehensive income, attributable to parent entity. Excludes changes in equity resulting from investments by owners and distributions to owners.

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