Realized and Net Change in Unrealized Gains (Losses) on Investments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Gain (Loss) on Investments [Line Items]
Realized Gains (Losses)	$ (30)	$ (695)	$ (8)	$ 5,612
Net Change in Unrealized Gains (Losses)on other investments	(825)	13	(454)	(6,491)
Total realized and net change in unrealized gains (losses)	$ (855)	$ (682)	$ (462)	$ (879)