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Income Taxes - Narrative (Details) - USD ($)	3 Months Ended		6 Months Ended
Income Taxes - Narrative (Details) - USD ($)	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Mar. 31, 2019
Related Party Transaction [Line Items]
Effective tax rate	7.70%	14.60%	10.50%	11.40%
Payable to related parties pursuant to tax receivable agreement	$ 101,322,000		$ 101,322,000		$ 69,636,000
Unrecognized tax positions	0		0
Tax Receivable Agreement
Related Party Transaction [Line Items]
Payable to related parties pursuant to tax receivable agreement	31,481,000		31,481,000
September 2019 Offering
Related Party Transaction [Line Items]
Deferred tax asset	41,130,000		41,130,000
Valuation allowance	$ 3,736,000		$ 3,736,000