Employee Benefit Plans (Details 5) (Stock options, USD $) In Millions, except Share data in Thousands, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Stock options
Summary of stock option activity
Options outstanding, beginning of period (in shares)	13,684	13,034	16,312
Granted (in shares)		3,718
Exercised (in shares)	(551)	(389)	(316)
Cancelled or expired (in shares)	(3,317)	(2,679)	(2,962)
Options outstanding, end of period (in shares)	9,816	13,684	13,034
Options exercisable, end of period (in shares)	7,056	9,355	10,867
Summary of stock option activity, Exercise Price
Options outstanding, beginning of period, Exercise Price (in dollars per share)	$ 16	$ 19	$ 19
Granted, Exercise Price (in dollars per share)		$ 8
Exercised, Exercise Price (in dollars per share)	$ 9	$ 6	$ 8
Cancelled or expired, Exercise Price (in dollars per share)	$ 15	$ 20	$ 22
Options outstanding, end of period, Exercise Price (in dollars per share)	$ 16	$ 16	$ 19
Options exercisable, end of period, Exercise Price (in dollars per share)	$ 19	$ 19	$ 20
Pretax intrinsic value of options exercised	$ 2.0	$ 1.1	$ 0.8
Tax benefit realized for the tax deduction from options exercised	0.5	0.3	0.2
Total fair value of options vested	$ 42.8	$ 60.5	$ 76.0