Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss)
Balance, beginning	$ 1,989	$ 17,744	$ 9,645
Other comprehensive income (loss) before reclassification	(14,119)	(18,791)	7,366
Amounts reclassified from accumulated other comprehensive income	4,748	3,036	733
Net current period other comprehensive income (loss)	(9,371)	(15,755)	8,099
Balance, end	(7,382)	1,989	17,744
Available-For-Sale Securities
Accumulated Other Comprehensive Income (Loss)
Balance, beginning	13,935	27,945	8,485
Other comprehensive income (loss) before reclassification	(13,113)	(13,968)	19,335
Amounts reclassified from accumulated other comprehensive income	817	(42)	125
Net current period other comprehensive income (loss)	(12,296)	(14,010)	19,460
Balance, end	1,639	13,935	27,945
Derivatives Used for Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss)
Balance, beginning	(11,946)	(10,201)	1,160
Other comprehensive income (loss) before reclassification	(1,006)	(4,823)	(11,969)
Amounts reclassified from accumulated other comprehensive income	3,931	3,078	608
Net current period other comprehensive income (loss)	2,925	(1,745)	(11,361)
Balance, end	$ (9,021)	$ (11,946)	$ (10,201)