CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Comprehensive income:
Net income	$ 118,403	$ 116,605
Derivative instruments:
Net fair value (decrease) increase, net of tax of $(2) and $4, respectively	(3)	7
Reclassification of gains to net income, net of tax of $(73) and $(74), respectively	(120)	(118)
Other comprehensive loss	(123)	(111)
Comprehensive income	$ 118,280	$ 116,494