Other Investments (Tables)

12 Months Ended

Dec. 31, 2014

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:

	Longest Maturity Date	Amortized Cost				Fair Value
		December 31,
(in millions)		2014		2013		2014		2013
Stocks	—	$	524	$	656	$	2,031	$	2,208
Municipal bonds	2054	681		675		822		756
U.S. government and agency securities	2045	777		902		836		947
Corporate bonds	2057	346		208		395		241
Short-term investments and receivables/payables	One-year	692		329		715		342
Total		$	3,020	$	2,770	$	4,799	$	4,494

Summary of Changes in the Fair Value of Trust

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

	Years ended December 31,
(in millions)	2014			2013			2012
Balance at beginning of period	$	4,494		$	4,048		$	3,592
Gross realized gains	197			300			73
Gross realized losses	(5		)	(32		)	(5		)
Unrealized gains, net	75			160			276
Other-than-temporary impairments	(14		)	(47		)	(36		)
Interest, dividends and other	118			113			113
Contributions	5			22			23
Income taxes	(62		)	(66		)	17
Decommissioning costs	(4		)	—			—
Administrative expenses and other	(5		)	(4		)	(5		)
Balance at end of period	$	4,799		$	4,494		$	4,048