Other Investments (Tables)

9 Months Ended

Sep. 30, 2012

Regulated Entity, Other Assets, Noncurrent [Abstract]

Amortized Cost and Fair Value of the Trust Investments

The following table sets forth amortized cost and fair value of the trust investments:

		Amortized Cost				Fair Value
(in millions)	Longest Maturity Dates	September 30, 2012		December 31, 2011		September 30, 2012		December 31, 2011
Stocks	—	$	957	$	865	$	2,227	$	1,899
Municipal bonds	2054	520		625		654		756
U.S. government and agency securities	2042	526		516		589		580
Corporate bonds	2054	287		259		374		317
Short-term investments and receivables/payables	One-year	147		38		153		40
Total		$	2,437	$	2,303	$	3,997	$	3,592

Summary of Changes in the Fair Value of Trust

The following table sets forth a summary of changes in the fair value of the trust:

	Three months ended September 30,						Nine months ended September 30,
(in millions)	2012			2011			2012			2011
Balance at beginning of period	$	3,810		$	3,657		$	3,592		$	3,480
Gross realized gains	13			46			54			81
Gross realized losses	—			(5		)	(5		)	(5		)
Unrealized gains (losses) – net	156			(305		)	272			(199		)
Other-than-temporary impairments	(7		)	(22		)	(30		)	(35		)
Interest, dividends, contributions and other	25			22			114			71
Balance at end of period	$	3,997		$	3,393		$	3,997		$	3,393