Thermon Group Holdings, Inc. Annual report pursuant to Section 13 and 15(d)

Stock-Based Compensation Expense Stock-Based Compensation Expense - Unvested Shares (Details)

Stock-Based Compensation Expense Stock-Based Compensation Expense - Unvested Shares (Details) - $ / shares	12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Exercised, weighted average exercise price (in dollars per share)			$ 21.51
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, beginning of period (in shares)	329,386	367,571	411,939
Forfeited (in shares)	(4,109)	(279)	(1,412)
Options outstanding, end of period (in shares)	139,485	329,386	367,571
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Options outstanding, weighted average exercise price (in dollars per share)	$ 12.30	$ 8.96	$ 9.12	$ 8.94
Exercised, weighted average exercise price (in dollars per share)	6.24	10.44	7.00
Forfeited, weighted average exercise price (in dollars per share)	$ 21.40	$ 21.52	$ 19.83
Unvested \| Stock Options
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, beginning of period (in shares)	9,500	19,000	37,829
Vested (in shares)	(9,500)	(9,500)	(17,417)
Forfeited (in shares)			(1,412)
Options outstanding, end of period (in shares)	0	9,500	19,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward]
Options outstanding, weighted average exercise price (in dollars per share)	$ 0	$ 5.89	$ 5.89	$ 8.86
Vested, weighted average exercise price (in dollars per share)	$ 5.89	$ 5.89	6.93
Forfeited, weighted average exercise price (in dollars per share)			$ 19.83