Regulatory Authorities - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012 EGL	Dec. 31, 2011 EGL	Dec. 31, 2012 ETC D
Regulatory Authorities [Line Items]
Maintenance of net capital of aggregate indebtedness, percent	6.67%
Regulatory net capital, value		$ 31,281	$ 67,893
Required net capital to be maintained	100
Regulatory net capital exceeding minimum net capital requirement		27,871	66,726
Tier 1 capital				5,000
Minimum liquid assets, amount				3,500
Coverage of operating expenses, days				90
Collateral held in a segregated account at a third-party depository institution				$ 10,000