Income Taxes - Narrative (Details) - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Dec. 31, 2018	Mar. 31, 2018
Income Tax Disclosure [Abstract]
Interest on income taxes accrued	$ 31.4	$ 12.9
Interest on income taxes accrued, acquisitions	23.2
Income tax penalties accrued	51.4	67.9
Tax Cuts and Jobs Act of 2017, provisional income tax benefit, remeasured deferred tax asset and liabilities		136.7
Penalties on income taxes accrued, acquisitions	15.8
Tax Cuts and Jobs Act of 2017, transition tax for accumulated foreign earnings	657.8	(644.7)
Tax Cuts and Jobs Act of 2017, transition tax for accumulated foreign earnings increase (decrease)	$ 13.1
Tax Cuts and Jobs Act of 2017, provisional income tax benefit, release of valuation allowance for foreign tax credits		$ 36.4