Debt Notes and Debentures (Details) (Successor [Member], USD $)																0 Months Ended	1 Months Ended
	Dec. 31, 2012		Dec. 31, 2012 Mortgage Bonds [Member]		Aug. 31, 2012 Corporate Debt Securities Three Point Zero Five Percent Debentures Due September 1, 2022 [Member]	Aug. 31, 2012 Corporate Debt Securities Four Point Three Seven Five Percent Debentures Due September 1, 2042 [Member]	Mar. 31, 2012 Corporate Debt Securities Three Point Zero Five Percent Debentures Due March 15, 2022	Mar. 31, 2012 Corporate Debt Securities Four Point Four Zero Percent Debentures Due March 15, 2042 [Member]	Aug. 31, 2011 Corporate Debt Securities Three Point Four Five Percent Debentures Due September 15, 2021 [Member]	Aug. 31, 2011 Corporate Debt Securities Four Point Nine Five Percent Debentures Due September 15, 2041 [Member]	May 31, 2011 Corporate Debt Securities Four Point One Zero Percent Debentures Due June 1, 2021 [Member]	May 31, 2011 Corporate Debt Securities Five Point Four Zero Percent Debentures Due June 1, 2041 [Member]	Sep. 30, 2010 Corporate Debt Securities Three Point Six Zero Percent Debentures Due September 1, 2020 [Member]	Sep. 30, 2010 Corporate Debt Securities Five Point Zero Five Percent Debentures Due March 1, 2041 [Member]	May 31, 2010 Corporate Debt Securities Five Point Seven Five Percent Debentures Due May 1, 2040 [Member]	Jan. 31, 2012 SEC Debt Shelf Registration	Jul. 31, 2012 SEC Debt Shelf Registration	Dec. 31, 2012 SEC Debt Shelf Registration	Dec. 31, 2012 Junior Subordinated Debt
Debt Instrument [Line Items]
Debentures issued amount					$ 600,000,000	$ 650,000,000	$ 625,000,000	$ 625,000,000	$ 450,000,000	$ 300,000,000	$ 250,000,000	$ 500,000,000	$ 250,000,000	$ 500,000,000	$ 750,000,000
Debentures interest rate					3.05%	4.375%	3.05%	4.40%	3.45%	4.95%	4.10%	5.40%	3.60%	5.05%	5.75%
Additional debt securities authorized for issuance by the Board of Managers																1,500,000,000	1,000,000,000
Remaining amount of debt securities that may be issued																		750,000,000
Subordinated notes related to financial covenants																			500,000,000
Total Debt excluding capital leases	$ 13,455,000,000	[1],[2]	$ 85,000,000	[3]

[1] Amount also excludes unamortized fair value adjustment under acquisition method accounting related to capital leases.

[2] Amount also excludes unamortized gains on interest rate swaps.

[3] Amounts represent debt outstanding and weighted average effective interest rates for 2012 and 2011, respectively. Maturities are as of December 31, 2012.