Condensed Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 9,745	$ 13,595	$ 17,956	$ 17,733
Other comprehensive income (loss):
Foreign currency translation	4	(20)	4	(24)
Total other comprehensive income (loss)	4	(20)	4	(24)
Comprehensive income	$ 9,749	$ 13,575	$ 17,960	$ 17,709

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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Amount, after deduction of tax, noncontrolling interests, dividends on preferred stock and participating securities; of income (loss) available to common shareholders.

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Amount after tax and reclassification adjustments of gain (loss) on foreign currency translation adjustments, foreign currency transactions designated and effective as economic hedges of a net investment in a foreign entity and intra-entity foreign currency transactions that are of a long-term-investment nature, attributable to parent entity.

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

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