CONSOLIDATED 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 Loss
Beginning Balance at Dec. 31, 2010	$ 502,678	$ 93,300	$ 187,071	$ 222,897	$ (590)
Balance (in shares) at Dec. 31, 2010		933,000
Comprehensive income:
Net income	51,006			51,006
Other comprehensive income	76				76
Common dividends declared to parent	(32,607)			(32,607)
Contribution of capital by parent	0		0
Ending Balance at Dec. 31, 2011	521,153	93,300	187,071	241,296	(514)
Balance (in shares) at Dec. 31, 2011		933,000
Comprehensive income:
Net income	49,951			49,951
Other comprehensive income	77				77
Common dividends declared to parent	(56,871)			(56,871)
Contribution of capital by parent	2,796		2,796
Ending Balance at Dec. 31, 2012	517,106	93,300	189,867	234,376	(437)
Balance (in shares) at Dec. 31, 2012	933,000	933,000
Comprehensive income:
Net income	59,468			59,468
Other comprehensive income	76				76
Common dividends declared to parent	(31,345)			(31,345)
Contribution of capital by parent	58,977		58,977
Ending Balance at Dec. 31, 2013	$ 604,282	$ 93,300	$ 248,844	$ 262,499	$ (361)
Balance (in shares) at Dec. 31, 2013	933,000	933,000