CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Comprehensive income:
Net income	$ 453,383	$ 458,076	$ 396,803
Derivative instruments:
Net fair value increase (decrease), net of tax of $5, $(5,708) and $(11,227), respectively	9	(9,311)	(18,328)
Reclassification of gains to net income, net of tax of $(294), $(725) and $(922), respectively	(476)	(1,183)	(1,506)
Other comprehensive income (loss)	(467)	(10,494)	(19,834)
Comprehensive income	$ 452,916	$ 447,582	$ 376,969