Income From Continuing Operations Per Common Share (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended
	Jun. 30, 2016	Jun. 30, 2015
Basic income from continuing operations per common share:
Income from continuing operations	$ 198	$ 207
Less: Income from continuing operations allocable to participating securities	(2)	(2)
Income from continuing operations allocable to common shares	$ 196	$ 205
Weighted average common shares outstanding	414	436
Basic income from continuing operations per common share (in dollars per share)	$ 0.47	$ 0.47
Diluted income from continuing operations per common share:
Income from continuing operations	$ 198	$ 207
Less: Income from continuing operations allocable to participating securities	(2)	(2)
Income from continuing operations allocable to common shares	$ 196	$ 205
Weighted average shares outstanding and common share equivalents:
Weighted average common shares outstanding	414	436
Weighted average effect of share-based payment awards	1	2
Denominator in calculation of diluted income per share	415	438
Diluted income from continuing operations per common share (in dollars per share)	$ 0.47	$ 0.47
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
Weighted average restricted stock awards considered participating securities	5	4