Other Investments (Tables)

6 Months Ended

Jun. 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	June 30, 2012		December 31, 2011		June 30, 2012		December 31, 2011
Stocks	—	$	953	$	865	$	2,090	$	1,899
Municipal bonds	2051	583		625		714		756
U.S. government and agency securities	2041	489		516		549		580
Corporate bonds	2054	310		259		382		317
Short-term investments and receivables/payables	One-year	71		38		75		40
Total		$	2,406	$	2,303	$	3,810	$	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 June 30,						Six months ended June 30,
(in millions)	2012			2011			2012			2011
Balance at beginning of period	$	3,853		$	3,619		$	3,592		$	3,480
Gross realized gains	15			12			40			35
Gross realized losses	(1		)	—			(5		)	—
Unrealized gains (losses) – net	(67		)	4			116			106
Other-than-temporary impairments	(19		)	(4		)	(23		)	(13		)
Interest, dividends, contributions and other	29			26			90			49
Balance at end of period	$	3,810		$	3,657		$	3,810		$	3,657