CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) [Abstract]
Net income	$ 21,067	$ 32,391	$ 79,968	$ 107,346
Amounts related to available-for-sale securities:
Change in net unrealized gains	(11,130)	(10,720)	(23,770)	22,465
Amounts related to cash flow hedges:
Change in net unrealized losses	(21,235)	97	(36,226)	(25,557)
Reclassification adjustment for amounts included in net income	7,183	5,826	20,494	15,932
Other comprehensive income (loss)	(25,182)	(4,797)	(39,502)	12,840
Comprehensive income (loss)	$ (4,115)	$ 27,594	$ 40,466	$ 120,186