CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 39,022	$ 30,547	$ 79,780	$ 81,521
Other comprehensive income (loss), net of tax effect:
Derivatives	14,561	63,202	(3,780)	41,137
Foreign currency items	(523)		(523)
Comprehensive income	$ 53,060	$ 93,749	$ 75,477	$ 122,658