Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Accumulated Other Comprehensive Income (Loss)
Balance, beginning			$ (7,382)	$ 1,989
Other comprehensive income (loss) before reclassification			9,418	11,411
Amounts reclassified from accumulated other comprehensive income (loss)			2,631	3,438
Net current period other comprehensive income (loss)	$ (1,032)	$ (3,575)	12,049	14,849
Balance, end	4,667	16,838	4,667	16,838
Available-For-Sale Securities
Accumulated Other Comprehensive Income (Loss)
Balance, beginning			1,639	13,935
Other comprehensive income (loss) before reclassification			10,520	18,755
Amounts reclassified from accumulated other comprehensive income (loss)			318	399
Net current period other comprehensive income (loss)			10,838	19,154
Balance, end	12,477	33,089	12,477	33,089
Derivatives Used for Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss)
Balance, beginning			(9,021)	(11,946)
Other comprehensive income (loss) before reclassification			(1,102)	(7,344)
Amounts reclassified from accumulated other comprehensive income (loss)			2,313	3,039
Net current period other comprehensive income (loss)			1,211	(4,305)
Balance, end	$ (7,810)	$ (16,251)	$ (7,810)	$ (16,251)