Income tax (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Dec. 31, 2014	Dec. 31, 2014	Dec. 31, 2013
Income Tax Disclosure [Abstract]
Effective Income Tax Rate		6.00%	9.70%
Release of prior year tax provisions	$ 1.9	$ 9.3
Release of prior year tax provisions basic earnings per share impact	$ 0.01	$ 0.04
Release of prior year tax provisions diluted earnings per share impact	$ 0.01	$ 0.04
Unrecognized Tax Benefits	222.0us-gaap_UnrecognizedTaxBenefits	222.0us-gaap_UnrecognizedTaxBenefits
Unrecognized Tax Benefits, Period Increase (Decrease)		42.0
Unrecognized tax benefit presented as a reduction to deferred tax assets for net operating loss carryforward and other tax credit carryforwards	$ 83.6	$ 83.6

Increase or (decrease) on basic earnings per common share from the release of prior year tax provisions

No definition available.

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- Definition

Increase or decrease in diluted earnings per share due to release of prior year tax provisions

+ References

No definition available.

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- Definition

Amount of unrecognized tax benefit presented as a reduction to deferred tax assets for net operating loss carryforward and other tax credit carryforwards.

+ References

No definition available.

+ Details

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- Definition

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 50

-Paragraph 12

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-Name Accounting Standards Codification

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 235

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.4-08.(h)(2))

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 08

-Paragraph h

-Subparagraph 2

-Article 4

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- Definition

Amount of increase (decrease) to previously recorded tax expense. Includes, but is not limited to, significant settlements of income tax disputes, and unusual tax positions or infrequent actions taken by the entity, including tax assessment reversal, and IRS tax settlement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

-Section 25

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=29652012&loc=d3e28446-109314

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- Definition

Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Unrecognized Tax Benefit

-URI http://asc.fasb.org/extlink&oid=6527854

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- Definition

The net amount of all increases and decreases in unrecognized tax benefits for the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 740

-SubTopic 10

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