CONDENSED CONSOLIDATED STATEMENT OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 36,102	$ 23,659	$ 115,882	$ 105,180
Other comprehensive income (loss), net of tax effect:
Derivatives	(18,384)	(33,166)	(22,164)	7,971
Foreign currency items	267		(256)
Comprehensive income (loss)	$ 17,985	$ (9,507)	$ 93,462	$ 113,151