Other Investments (Tables)

3 Months Ended

Mar. 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 Dates	Amortized Cost				Fair Value
(in millions)		March 31, 2014		December 31, 2013		March 31, 2014		December 31, 2013
Stocks	—	$	668	$	656	$	2,234	$	2,208
Municipal bonds	2051	725		675		838		756
U.S. government and agency securities	2044	812		902		864		947
Corporate bonds	2054	253		208		296		241
Short-term investments and receivables/payables	One-year	342		329		355		342
Total		$	2,800	$	2,770	$	4,587	$	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 trust:

	Three months ended March 31,
(in millions)	2014			2013
Balance at beginning of period	$	4,494		$	4,048
Gross realized gains	10			5
Gross realized losses	—			(1		)
Unrealized gains, net	62			176
Other-than-temporary impairments	(3		)	(8		)
Interest, dividends, contributions and other	24			26
Balance at end of period	$	4,587		$	4,246