Related Party Transactions (Narratives) (Details) - USD ($) $ in Millions	3 Months Ended
	Jun. 30, 2021	Jun. 30, 2020
Sac Holdings, Mercury, Four Sac, Five Sac, Galaxy and Private Mini [Member]
Property Management Fee [Abstract]
Property Management Fee Revenue	$ 11.3	$ 10.1
Sac Holdings, Mercury, Four Sac, Five Sac, Galaxy and Private Mini [Member] | Minimum [Member]
Property Management Fee [Abstract]
Management fee rate	4.00%
Sac Holdings, Mercury, Four Sac, Five Sac, Galaxy and Private Mini [Member] | Maximum [Member]
Property Management Fee [Abstract]
Management fee rate	10.00%
Sac Holdings, Four Sac, Five Sac, Galaxy, and Private Mini [Member]
Related party costs and expenses:
Revenue, excluding dealer agreement commissions and expenses	$ 7.2
Cash flow, related party	6.4
Revenue generated by the dealer agreement from related parties	$ 108.6