CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) [Abstract]
Net income	$ 24,944	$ 36,564	$ 58,901	$ 74,955
Amounts related to available-for-sale securities:
Change in net unrealized gains	(18,747)	16,492	(12,640)	33,185
Amounts related to cash flow hedges:
Change in net unrealized losses	3,400	(12,998)	(14,991)	(25,654)
Reclassification adjustment for amounts included in net income	6,863	5,384	13,311	10,106
Other comprehensive income (loss)	(8,484)	8,878	(14,320)	17,637
Comprehensive income	$ 16,460	$ 45,442	$ 44,581	$ 92,592