CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Comprehensive income (loss)
Net income	$ 24,702	$ 40,037	$ 89,514	$ 128,542
Amounts related to available-for-sale securities:
Change in net unrealized gains	(27,539)	66,910	(104,037)	134,583
Amounts related to cash flow hedges:
Change in net unrealized gains (losses)	(10,867)	(8,454)	9,136	(25,539)
Reclassification adjustment for amounts included in net income	3,698	4,835	13,548	14,630
Other comprehensive income	(34,708)	63,291	(81,353)	123,674
Comprehensive income (loss)	$ (10,006)	$ 103,328	$ 8,161	$ 252,216