Consolidated Statements of Comprehensive Income (Unaudited) - 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	$ 39,304	$ 29,244	$ 135,063	$ 100,535
Other comprehensive income, net of tax:
Unrealized gains (losses) on available-for-sale securities, net of taxes of $25 and $88 for the three months ended September 30, 2017 and 2016, respectively, and $257 and $5 for the nine months ended September 30, 2017 and 2016, respectively	40	(142)	416	(6)
Unrealized losses on hedging derivatives, net of taxes of $20 and $2 for the three months ended September 30, 2017 and 2016, respectively, and $65 and $203 for the nine months ended September 30, 2017 and 2016, respectively	(30)	(4)	(104)	(328)
Comprehensive income	$ 39,314	$ 29,098	$ 135,375	$ 100,201

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 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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Amount after tax, before reclassification adjustments, of unrealized holding gain (loss) on available-for-sale securities.

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