Significant Accounting Policies - Investments in Unconsolidated Entities (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Mar. 31, 2021
Investments in Unconsolidated Entities
Carrying value	$ 21,029	$ 22,719
Water Services and Land Company No. 1 | Water solutions | Operating segment
Investments in Unconsolidated Entities
Ownership interest	50.00%
Carrying value	$ 14,889	15,832
Water Services and Land Company No. 2 | Water solutions | Operating segment
Investments in Unconsolidated Entities
Ownership interest	50.00%
Carrying value	$ 2,047	2,284
Water Services and Land Company No. 3 | Water solutions | Operating segment
Investments in Unconsolidated Entities
Ownership interest	10.00%
Carrying value	$ 2,897	3,254
Aircraft Company | Corporate and other | Operating segment
Investments in Unconsolidated Entities
Ownership interest	50.00%
Carrying value	$ 640	748
Water Services Company | Water solutions | Operating segment
Investments in Unconsolidated Entities
Ownership interest	50.00%
Carrying value	$ 414	424
Natural Gas Liquids Terminal Company | Liquids logistics | Operating segment
Investments in Unconsolidated Entities
Ownership interest	50.00%
Carrying value	$ 142	$ 177