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 Income And Comprehensive Income [Abstract]
Net income	$ 16,752	$ 16,440	$ 57,002	$ 65,423
Amounts related to available-for-sale securities:
Change in net unrealized gains	(7,072)	(19,155)	(14,496)	10,245
Amounts related to cash flow hedges:
Change in net unrealized gains (losses)	1,827	12,558	3,541	(41,714)
Reclassification adjustment for amounts included in net income	(3,213)	4,927	(2,207)	16,107
Other comprehensive income (loss)	(8,458)	(1,670)	(13,162)	(15,362)
Comprehensive income	$ 8,294	$ 14,770	$ 43,840	$ 50,061

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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The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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

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Amount after tax of reclassification adjustment from accumulated other comprehensive income of accumulated gain (loss) realized from derivative instruments designated and qualifying as the effective portion of cash flow hedges and an entity's share of an equity investee's deferred hedging gain (loss).

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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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