CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (UNAUDITED) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Comprehensive income:
Net income	$ 5,742	$ 8,478	$ 20,620	$ 23,121
Derivative instruments:
Reclassification of losses to net income, net of tax of $12 for the three months ended June 30, 2012 and 2011, and $25 for the six months ended June 30, 2012 and 2011	19	19	38	38
Other comprehensive income	19	19	38	38
Comprehensive income	$ 5,761	$ 8,497	$ 20,658	$ 23,159