Condensed Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 133,722	$ 51,257	$ 319,368	$ 125,406
Other comprehensive income (loss), net of tax:
Foreign currency translation adjustments	343	(165)	500	(402)
Net change in unrealized gains (losses) on available-for-sale securities	(165)	(113)	(100)	94
Other comprehensive income (loss)	178	(278)	400	(308)
Comprehensive income	$ 133,900	$ 50,979	$ 319,768	$ 125,098

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 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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