Income Taxes - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Taxes [Line Items]
Securities transactions income tax expense	$ 147,000	$ 1,720,000	$ 560,000
Recognition of Interest and penalties related to unrecognized tax benefits	$ 0	$ 0	$ 0
Minimum [Member]
Income Taxes [Line Items]
Year under examination	2011
Maximum [Member]
Income Taxes [Line Items]
Year under examination	2013