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, 2011	$ 1,076,859	$ 0	$ 783,162	$ 295,201	$ (1,504)
Beginning 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
Comprehensive income:
Net income	95,177			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
Comprehensive income:
Net income	129,852			129,852
Other comprehensive income	172				172
Common dividends declared to parent	(93,243)			(93,243)
Contribution of capital by parent	160,000		160,000
Ending Balance at Dec. 31, 2014	$ 1,560,472	$ 0	$ 1,165,463	$ 395,998	$ (989)
Ending Balance (in shares) at Dec. 31, 2014	100	100