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 Income (Loss)
Beginning Balance at Dec. 31, 2011	$ 4,305,718	$ 0	$ 3,316,386	$ 1,001,709	$ (12,377)
Balance (in shares) at Dec. 31, 2011		100
Increase (Decrease) in Stockholder's Equity
Net income	458,076			458,076
Other comprehensive income (loss)	(10,494)				(10,494)
Common dividends declared to parent	(266,848)			(266,848)
Contribution of capital by parent	99,283		99,283
Ending Balance at Dec. 31, 2012	4,585,735	0	3,415,669	1,192,937	(22,871)
Balance (in shares) at Dec. 31, 2012		100
Increase (Decrease) in Stockholder's Equity
Net income	453,383			453,383
Other comprehensive income (loss)	(467)				(467)
Common dividends declared to parent	(262,273)			(262,273)
Contribution of capital by parent	25,621		25,621
Ending Balance at Dec. 31, 2013	4,801,999	0	3,441,290	1,384,047	(23,338)
Balance (in shares) at Dec. 31, 2013	100	100
Increase (Decrease) in Stockholder's Equity
Net income	455,188			455,188
Other comprehensive income (loss)	(540)				(540)
Common dividends declared to parent	(452,306)			(452,306)
Contribution of capital by parent	81,498		81,498
Ending Balance at Dec. 31, 2014	$ 4,885,839	$ 0	$ 3,522,788	$ 1,386,929	$ (23,878)
Balance (in shares) at Dec. 31, 2014	100	100