Benefit Plans Benefit Plans (401K Plan) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2012
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Employer contributions to 401k plan	$ 12.3	$ 11.7	$ 11.1
Maximum [Member]
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items]
Defined contribution plan employer contributions, percentage of participants' wages	2.00%