Earnings Per Share (Tables)

3 Months Ended

Mar. 31, 2013

Earnings Per Share [Abstract]

Schedule of computation of basic and diluted earnings per share

Computation of Earnings Per Share

	First Quarter
	2013			2012
	(in millions, except per share amounts)
Basic earnings per share ("EPS"):
Net income (loss) attributable to AGL	$	(144	)	$	(483	)
Less: Distributed and undistributed income (loss) available to nonvested shareholders	0			0
Distributed and undistributed income (loss) available to common shareholders of AGL and subsidiaries, basic	$	(144	)	$	(483	)
Basic shares	193.9			182.4
Basic EPS	$	(0.74	)	$	(2.65	)
Diluted EPS:
Distributed and undistributed income (loss) available to common shareholders of AGL and subsidiaries, basic	$	(144	)	$	(483	)
Plus: Re-allocation of undistributed income (loss) available to nonvested shareholders of AGL and subsidiaries	—			—
Distributed and undistributed income (loss) available to common shareholders of AGL and subsidiaries, diluted	$	(144	)	$	(483	)
Basic shares	193.9			182.4
Effect of dilutive securities:
Options and restricted stock awards	—			—
Equity units	—			—
Diluted shares	193.9			182.4
Diluted EPS	$	(0.74	)	$	(2.65	)
Potentially dilutive securities excluded from computation of EPS because of antidilutive effect	5.1			18.7