Regulatory Authorities - Additional Information (Detail)	Sep. 30, 2015 USD ($)	Jun. 30, 2015 USD ($)
LFNY [Member]
Regulatory Requirements [Line Items]
Specified fixed percentage, minimum required capital	6.67%
Minimum net capital requirement as defined under securities exchange act	$ 100,000
Regulatory capital	207,189,000
Regulatory capital in excess of minimum requirement	$ 203,374,000
Aggregate indebtedness to net capital ratio	0.28
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	$ 119,490,000
Regulatory capital in excess of minimum requirement	101,713,000
CFLF [Member]
Regulatory Requirements [Line Items]
Regulatory capital	134,142,000
Regulatory capital in excess of minimum requirement	89,369,000
Combined European Regulated Group [Member]
Regulatory Requirements [Line Items]
Regulatory capital		$ 179,780,000
Regulatory capital in excess of minimum requirement		$ 115,014,000
Other U.S. and Non-U.S. Subsidiaries [Member]
Regulatory Requirements [Line Items]
Regulatory capital	108,221,000
Regulatory capital in excess of minimum requirement	$ 75,949,000