Stockholders' Equity

3 Months Ended

Mar. 31, 2013

Disclosure Text Block [Abstract]

Stockholders' Equity

9.  Stockholders' Equity

The reconciliation between basic and diluted earnings per share attributable to common stockholders is as follows:

		Three Months Ended
		March 31,
millions except per-share amounts		2013		2012
Net income (loss)
	Net income (loss) attributable to common stockholders	$	460	$	2,156
	Less undistributed income allocated to participating securities		3		12
	Basic	$	457	$	2,144
	Diluted	$	457	$	2,144
Shares
	Average number of common shares outstanding—basic		501		499
	Dilutive effect of stock options		2		2
	Average number of common shares outstanding—diluted		503		501
	Excluded (1)		4		4
Net income (loss) per common share
	Basic	$	0.91	$	4.30
	Diluted	$	0.91	$	4.28
	Dividends per common share	$	0.09	$	0.09

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(1)Inclusion of certain shares would have had an anti-dilutive effect.