STATEMENTS OF COMMON STOCKHOLDER'S EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Total	Common stock	Additional Paid In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Beginning Balance at Dec. 31, 2010	$ 962,113	$ 0	$ 693,531	$ 270,257	$ (1,675)
Beginning Balance (in shares) at Dec. 31, 2010		100
Comprehensive income:
Net income	89,901			89,901
Other comprehensive income	171				171
Common dividends declared to parent	(64,957)			(64,957)
Contribution of capital by parent	89,631		89,631
Ending Balance at Dec. 31, 2011	1,076,859	0	783,162	295,201	(1,504)
Ending Balance (in shares) at Dec. 31, 2011		100
Comprehensive income:
Net income	106,369			106,369
Other comprehensive income	172				172
Common dividends declared to parent	(66,469)			(66,469)
Contribution of capital by parent	60,024		60,024
Ending Balance at Dec. 31, 2012	1,176,955	0	843,186	335,101	(1,332)
Ending Balance (in shares) at Dec. 31, 2012	100	100
Comprehensive income:
Net income	95,177
Other comprehensive income	171				171
Common dividends declared to parent	(70,889)			(70,889)
Contribution of capital by parent	162,277		162,277
Ending Balance at Dec. 31, 2013	$ 1,363,691	$ 0	$ 1,005,463	$ 359,389	$ (1,161)
Ending Balance (in shares) at Dec. 31, 2013	100	100