Income tax (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Dec. 31, 2013	Dec. 31, 2013	Dec. 31, 2012
Income Tax Disclosure [Abstract]
Effective Income Tax Rate		9.70%	34.10%
Tax Adjustments, Settlements, and Unusual Provisions	$ 6.2
Unrecognized Tax Benefits	179.2	179.2
Unrecognized Tax Benefits, Period Increase (Decrease)		$ 3.5