Subsequent Events (Details) - USD ($)									12 Months Ended
	Jun. 02, 2022	May 19, 2022	May 05, 2022	Apr. 21, 2022	Jan. 25, 2022	Jan. 04, 2022	Sep. 08, 2021	Jul. 30, 2021	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Subsequent Event
Repayment of long-term debt borrowings									$ 230,317,537	$ 99,418,395	$ 63,968,414
Dividends declared (in dollars per share)						$ 1.00		$ 1.00
Dividends declared						$ 40,100,000		$ 40,400,000
Dividends paid in cash					$ 39,900,000		$ 40,200,000		80,082,210
Dividends payable					$ 200,000		$ 200,000		494,180
Proceeds from sale of vessel									$ 90,460,363
Commercial Financing
Subsequent Event
Loan term period									3 years
Subsequent events
Subsequent Event
Dividends declared (in dollars per share)			$ 2.50
Dividends declared			$ 100,300,000
Dividends paid in cash	$ 99,700,000
Dividends payable	$ 600,000
Subsequent events | Commercial Financing
Subsequent Event
Repayment of long-term debt borrowings				$ 11,100,000
Subsequent events | KEXIM Direct Financing
Subsequent Event
Repayment of long-term debt borrowings				11,100,000
Subsequent events | K-sure Insured
Subsequent Event
Repayment of long-term debt borrowings				2,800,000
Subsequent events | Cougar Japanese Financing
Subsequent Event
Loan term period		10 years
Estimated financing cost to be incurred		$ 300,000
Percentage of broker commission fee payable		1.25%
Brokerage Commission Fee on delivery Purchase Option (as a percent)		0.50%
Periodic principal payment amount		$ 900,000
Principal payment frequency		quarterly
Balloon payment amount		$ 14,000,000.0
Subsequent events | Cougar Japanese Financing | three-month SOFR
Subsequent Event
Margin (as a percent)		2.45%
Subsequent events | 2015 AR Facility
Subsequent Event
Repayment of long-term debt borrowings				$ 25,000,000.0
Subsequent events | Cougar LPG Transport LLC
Subsequent Event
Deposit retained by buyer used for purchase payment		$ 20,000,000.0
Value of vessel transferred		$ 70,000,000.0
Term of Charter Agreement		10 years
Period until purchase option exercisable		3 years
Proceeds from sale of vessel		$ 50,000,000.0
Deposit retained by buyer		20,000,000.0
Subsequent events | Cougar LPG Transport LLC | 2015 AR Facility
Subsequent Event
Repayment of debt		$ 20,000,000.0