Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss)
Balance, beginning			$ (7,382)	$ 1,989
Other comprehensive income (loss) before reclassification			11,127	16,302
Amounts reclassified from accumulated other comprehensive income (loss)			1,954	2,122
Net current period other comprehensive income (loss)	$ 10,111	$ 15,092	13,081	18,424
Balance, end	5,699	20,413	5,699	20,413
Available-For-Sale Securities
Accumulated Other Comprehensive Income (Loss)
Balance, beginning			1,639	13,935
Other comprehensive income (loss) before reclassification			12,256	24,846
Amounts reclassified from accumulated other comprehensive income (loss)			365	35
Net current period other comprehensive income (loss)			12,621	24,881
Balance, end	14,260	38,816	14,260	38,816
Derivatives Used for Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss)
Balance, beginning			(9,021)	(11,946)
Other comprehensive income (loss) before reclassification			(1,129)	(8,544)
Amounts reclassified from accumulated other comprehensive income (loss)			1,589	2,087
Net current period other comprehensive income (loss)			460	(6,457)
Balance, end	$ (8,561)	$ (18,403)	$ (8,561)	$ (18,403)