CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 147,142	$ 106,105	$ 218,990	$ 201,971
Net change in foreign currency translation adjustment	213	(759)	622	283
Change in unrealized gains (losses) on investments, net of tax	192	186	276	57
Other comprehensive income (loss)	405	(573)	898	340
Comprehensive income	$ 147,547	$ 105,532	$ 219,888	$ 202,311

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.

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