Regulatory Authorities - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014
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
Regulatory capital	128,382
Regulatory capital in excess of minimum requirement	123,999
Aggregate indebtedness to net capital ratio	0.51
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	86,273
Regulatory capital in excess of minimum requirement	68,683
CFLF [Member]
Regulatory Requirements [Line Items]
Regulatory capital	134,708
Regulatory capital in excess of minimum requirement	87,130
Combined European Regulated Group [Member]
Regulatory Requirements [Line Items]
Regulatory capital	180,047
Regulatory capital in excess of minimum requirement	104,309
Other U.S. and Non-U.S. Subsidiaries [Member]
Regulatory Requirements [Line Items]
Regulatory capital	111,224
Regulatory capital in excess of minimum requirement	$ 84,699