Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Schedule of computation of basic and diluted earnings per share

Computation of Earnings Per Share

	Year Ended December 31,
	2018		2017		2016
	(in millions, except per share amounts)
Basic EPS:
Net income (loss) attributable to AGL	$	521	$	730	881
Less: Distributed and undistributed income (loss) available to nonvested shareholders	1		1		1
Distributed and undistributed income (loss) available to common shareholders of AGL and subsidiaries, basic	$	520	$	729	880
Basic shares	110.0		120.6		133.0
Basic EPS	$	4.73	$	6.05	$	6.61
Diluted EPS:
Distributed and undistributed income (loss) available to common shareholders of AGL and subsidiaries, basic	$	520	$	729	$	880
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	$	520	$	729	$	880
Basic shares	110.0		120.6		133.0
Dilutive securities:
Options and restricted stock awards	1.3		1.7		1.1
Diluted shares	111.3		122.3		134.1
Diluted EPS	$	4.68	$	5.96	$	6.56
Potentially dilutive securities excluded from computation of EPS because of antidilutive effect	0.1		0.1		0.3

Schedule of antidilutive securities excluded from computation of earnings per share

Computation of Earnings Per Share

	Year Ended December 31,
	2018		2017		2016
	(in millions, except per share amounts)
Basic EPS:
Net income (loss) attributable to AGL	$	521	$	730	881
Less: Distributed and undistributed income (loss) available to nonvested shareholders	1		1		1
Distributed and undistributed income (loss) available to common shareholders of AGL and subsidiaries, basic	$	520	$	729	880
Basic shares	110.0		120.6		133.0
Basic EPS	$	4.73	$	6.05	$	6.61
Diluted EPS:
Distributed and undistributed income (loss) available to common shareholders of AGL and subsidiaries, basic	$	520	$	729	$	880
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	$	520	$	729	$	880
Basic shares	110.0		120.6		133.0
Dilutive securities:
Options and restricted stock awards	1.3		1.7		1.1
Diluted shares	111.3		122.3		134.1
Diluted EPS	$	4.68	$	5.96	$	6.56
Potentially dilutive securities excluded from computation of EPS because of antidilutive effect	0.1		0.1		0.3