CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Changes in unrealized gains (losses) - taxes (benefits)	$ 10,569	$ (20,545)	$ 23,614	$ (11,586)
Reclassification adjustment for net losses (gains) realized in net income - taxes	703	1,052	2,353	2,309
Changes in market value of derivatives - benefits	(20,974)	(12,325)	(15,046)	(8,933)
Reclassification adjustment for net losses realized in net income - benefits	$ (14,273)	$ (416)	$ (14,278)	$ (1,525)