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	$ 129,852us-gaap_NetIncomeLoss	$ 95,177us-gaap_NetIncomeLoss	$ 106,369us-gaap_NetIncomeLoss
Derivative instruments:
Reclassification of losses to net income, net of tax of $96, $97 and $97, respectively	172	171	172
Other comprehensive income	172	171	172
Comprehensive income	$ 130,024us-gaap_ComprehensiveIncomeNetOfTax	$ 95,348us-gaap_ComprehensiveIncomeNetOfTax	$ 106,541us-gaap_ComprehensiveIncomeNetOfTax

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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