Consolidated Quarterly Results of Operations (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2020	Mar. 31, 2019	Mar. 31, 2018
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 302,694	$ 333,515	$ 272,810	$ 250,349	$ 291,378	$ 298,013	$ 274,992	$ 220,002	$ 1,159,368	$ 1,084,385	$ 963,364
Total operating expenses	234,039	265,499	227,657	202,572	230,827	235,770	218,817	179,874	929,767	865,288	748,951
Operating income	68,655	68,016	45,153	47,777	60,551	62,243	56,175	40,128	$ 229,601	$ 219,097	$ 214,413
Net income attributable to Houlihan Lokey, Inc.	$ 59,014	$ 48,894	$ 33,110	$ 42,775	$ 45,348	$ 43,957	$ 40,119	$ 29,682
Earnings per share
Basic (in usd per share)	$ 0.95	$ 0.79	$ 0.53	$ 0.69	$ 0.74	$ 0.71	$ 0.64	$ 0.47	$ 2.96	$ 2.56	$ 2.76
Diluted (in usd per share)	0.90	0.75	0.50	0.65	0.69	0.67	0.61	0.45	$ 2.80	$ 2.42	$ 2.60
Dividends declared per share of common stock (in usd per share)	$ 0.31	$ 0.31	$ 0.31	$ 0.31	$ 0.31	$ 0.27	$ 0.27	$ 0.27