Consolidated Statement of Owner's Equity Consolidated Statement of Owner's Equity (USD $) In Thousands	Total	Member's Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period at Dec. 31, 2010		$ 1,727,434	$ 2,117,153	$ 173
Cash contributions from parent	115,000	115,000
Non-cash contributions from parent		0
Non-cash return of capital		(546)
Net income	279,658		279,658
Cash distributions to parent	(219,000)		(219,000)
Equity interest in unrealized gain (loss) on interest rate hedge	(519)			(519)
Balance at end of period at Dec. 31, 2011	4,019,353	1,841,888	2,177,811	(346)
Cash contributions from parent	150,000	150,000
Non-cash contributions from parent		1,524
Non-cash return of capital		0
Net income	272,466		272,466
Cash distributions to parent	(246,259)		(246,259)
Equity interest in unrealized gain (loss) on interest rate hedge	(376)			(376)
Balance at end of period at Dec. 31, 2012	4,196,708	1,993,412	2,204,018	(722)
Cash contributions from parent	264,000	264,000
Non-cash contributions from parent		87
Non-cash return of capital		0
Net income	374,026		374,026
Cash distributions to parent	(250,000)		(250,000)
Equity interest in unrealized gain (loss) on interest rate hedge	464			464
Balance at end of period at Dec. 31, 2013	$ 4,585,285	$ 2,257,499	$ 2,328,044	$ (258)