CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) [Abstract]
Net income	$ 16,440	$ 21,067	$ 65,423	$ 79,968
Amounts related to available-for-sale securities:
Change in net unrealized gains	(19,155)	(11,130)	10,245	(23,770)
Amounts related to cash flow hedges:
Change in net unrealized losses	12,558	(21,235)	(41,714)	(36,226)
Reclassification adjustment for amounts included in net income	4,927	7,183	16,107	20,494
Other comprehensive income (loss)	(1,670)	(25,182)	(15,362)	(39,502)
Comprehensive income (loss)	$ 14,770	$ (4,115)	$ 50,061	$ 40,466