Regulatory Authorities - Additional Information (Detail) - USD ($)	Jun. 30, 2021	Mar. 31, 2021
LFNY [Member]
Regulatory Requirements [Line Items]
Specified fixed percentage, minimum required capital	6.67%
Minimum net capital requirement as defined under exchange act	$ 5,000
Regulatory capital	145,599,000
Regulatory capital in excess of minimum requirement	$ 141,258,000
Aggregate indebtedness to net capital ratio	0.45
LFNY [Member] | Maximum [Member]
Regulatory Requirements [Line Items]
Aggregate indebtedness to net capital ratio	15
U.K. Subsidiaries [Member]
Regulatory Requirements [Line Items]
Regulatory capital	$ 168,980,000
Regulatory capital in excess of minimum requirement	145,509,000
CFLF [Member]
Regulatory Requirements [Line Items]
Regulatory capital	150,047,000
Regulatory capital in excess of minimum requirement	81,204,000
Combined European Regulated Group [Member]
Regulatory Requirements [Line Items]
Regulatory capital		$ 176,304,000
Regulatory capital in excess of minimum requirement		$ 59,073,000
Other U.S. and Non-U.S. Subsidiaries [Member]
Regulatory Requirements [Line Items]
Regulatory capital	232,926,000
Regulatory capital in excess of minimum requirement	$ 203,719,000