Regulatory Authorities - Additional Information (Detail) - USD ($)	Sep. 30, 2019	Jun. 30, 2019
LFNY [Member]
Regulatory Requirements [Line Items]
Specified fixed percentage, minimum required capital	6.67%
Minimum net capital requirement as defined under exchange act	$ 100,000
Regulatory capital	133,716,000
Regulatory capital in excess of minimum requirement	$ 128,376,000
Aggregate indebtedness to net capital ratio	0.60
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	$ 148,962,000
Regulatory capital in excess of minimum requirement	132,957,000
CFLF [Member]
Regulatory Requirements [Line Items]
Regulatory capital	161,499,000
Regulatory capital in excess of minimum requirement	106,159,000
Combined European Regulated Group [Member]
Regulatory Requirements [Line Items]
Regulatory capital		$ 211,440,000
Regulatory capital in excess of minimum requirement		$ 107,119,000
Other U.S. and Non-U.S. Subsidiaries [Member]
Regulatory Requirements [Line Items]
Regulatory capital	153,873,000
Regulatory capital in excess of minimum requirement	$ 125,826,000