Earnings Per Share (Tables)

12 Months Ended

Dec. 31, 2019

Earnings Per Share [Abstract]

Schedule of computation of basic and diluted earnings per share

Computation of Earnings Per Share 

	Year Ended December 31,
	2019		2018		2017
	(in millions, except per share amounts)
Basic EPS:
Net income (loss) attributable to AGL	$	402	$	521	730
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	$	401	$	520	729
Basic shares	99.3		110.0		120.6
Basic EPS	$	4.04	$	4.73	$	6.05
Diluted EPS:
Distributed and undistributed income (loss) available to common shareholders of AGL and subsidiaries, basic	$	401	$	520	$	729
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	$	401	$	520	$	729
Basic shares	99.3		110.0		120.6
Dilutive securities:
Options and restricted stock awards	0.9		1.3		1.7
Diluted shares	100.2		111.3		122.3
Diluted EPS	$	4.00	$	4.68	$	5.96
Potentially dilutive securities excluded from computation of EPS because of antidilutive effect	—		0.1		0.1

Schedule of antidilutive securities excluded from computation of earnings per share

Computation of Earnings Per Share 

	Year Ended December 31,
	2019		2018		2017
	(in millions, except per share amounts)
Basic EPS:
Net income (loss) attributable to AGL	$	402	$	521	730
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	$	401	$	520	729
Basic shares	99.3		110.0		120.6
Basic EPS	$	4.04	$	4.73	$	6.05
Diluted EPS:
Distributed and undistributed income (loss) available to common shareholders of AGL and subsidiaries, basic	$	401	$	520	$	729
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	$	401	$	520	$	729
Basic shares	99.3		110.0		120.6
Dilutive securities:
Options and restricted stock awards	0.9		1.3		1.7
Diluted shares	100.2		111.3		122.3
Diluted EPS	$	4.00	$	4.68	$	5.96
Potentially dilutive securities excluded from computation of EPS because of antidilutive effect	—		0.1		0.1