Condensed Consolidated Balance Sheets (Parenthetical) (USD $) In Millions, except Share data, unless otherwise specified	Jun. 30, 2012	Mar. 31, 2012
Condensed Consolidated Balance Sheets [Abstract]
Accumulated depreciation	$ 720	$ 707
Preferred stock, par value
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued
Preferred stock, shares outstanding
Common stock, par value	$ 0.10	$ 0.10
Common stock, shares authorized	1,100,000,000	1,100,000,000
Common stock, shares issued	589,695,081	589,695,081
Common stock, shares outstanding	463,158,153	466,183,134
Treasury stock, shares	126,536,928	123,511,947