Severance, Exit Costs and Asset Impairments Severance, Exit Costs and Asset Impairments (Details) (Lease and access exit costs [Member], USD $) In Millions, unless otherwise specified	6 Months Ended
	Sep. 30, 2014
Minimum [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring And Related Cost Expected Future Cost	$ 75
Maximum [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring And Related Cost Expected Future Cost	$ 175