Supplemental Cash Flow Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Supplemental Cash Flow Information [Abstract]
Interest paid	$ 1,647	$ 2,092
Income taxes paid, net of refunds	138	151
Reclassification of available-for-sale securities to equity method investment	10,858	27,647
Partnership interest exchanged for marketable securities	25,000	0
Securities received in exchange for financial instrument obligations	76	19,341
Securities delivered in exchange for settlement of financial instrument obligations	76	0
Restricted stock awards surrendered to satisfy tax withholding obligations upon vesting	32	14
Contribution of advances by non-controlling interest	$ 0	$ 268