Related Party Transactions (Narratives) (Details) - Sac Holdings, Mercury, Four Sac, Five Sac, Galaxy and Private Mini [Member] - USD ($) $ in Millions	12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Property Management Fee [Abstract]
Management fees received exclusive of reimbursed expenses	$ 30.0	$ 29.5	$ 27.8
Related party costs and expenses:
Revenue, excluding dealer agreement commissions and expenses	24.0
Expenses, related parties	2.7
Cash flow, related party	21.3
Revenue, generated by the dealer agreement from related parties	288.2
Commission expenses, generated from dealer agreement with related parties	$ 61.4
Minimum [Member]
Property Management Fee [Abstract]
Management fee rate	4.00%	4.00%	4.00%
Maximum [Member]
Property Management Fee [Abstract]
Management fee rate	10.00%	10.00%	10.00%