Income From Continuing Operations Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2015	Dec. 31, 2014
Basic income from continuing operations per common share:
Income from continuing operations	$ 219	$ 218	$ 598	$ 665
Less: Income from continuing operations allocable to participating securities	(2)	(2)	(6)	(7)
Income from continuing operations allocable to common shares	$ 217	$ 216	$ 592	$ 658
Weighted average common shares outstanding	420	440	431	440
Basic income from continuing operations per common share (in dollars per share)	$ 0.52	$ 0.49	$ 1.37	$ 1.50
Diluted income from continuing operations per common share:
Income from continuing operations	$ 219	$ 218	$ 598	$ 665
Less: Income from continuing operations allocable to participating securities	(2)	(2)	(6)	(7)
Income from continuing operations allocable to common shares	$ 217	$ 216	$ 592	$ 658
Weighted average shares outstanding and common share equivalents:
Weighted average common shares outstanding	420	440	431	440
Weighted average effect of share-based payment awards	1	1	1	1
Denominator in calculation of diluted income per share	421	441	432	441
Diluted income from continuing operations per common share (in dollars per share)	$ 0.52	$ 0.49	$ 1.37	$ 1.49
Income from continuing operations per common share, Other disclosures [Abstract]
Number of anti-dilutive restricted stock awards and options excluded from the calculation	2	1	2	1
Weighted average restricted stock awards considered participating securities	4	5	4	4