CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Comprehensive income:
Net income	$ 22,013	$ 22,200	$ 52,242	$ 42,820
Derivative instruments:
Reclassification of losses to net income, net of tax of $12, $12, $38 and $37, respectively.	20	20	57	58
Other comprehensive income	20	20	57	58
Comprehensive income	$ 22,033	$ 22,220	$ 52,299	$ 42,878