CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Comprehensive income:
Net income	$ 70,642	$ 59,468	$ 49,951
Derivative instruments:
Reclassification of losses to net income, net of tax of $51, $51 and $51, respectively.	76	76	77
Other comprehensive income	76	76	77
Comprehensive income	$ 70,718	$ 59,544	$ 50,028