Investments - Additional Information (Detail) (USD $) Share data in Thousands, except Per Share data, unless otherwise specified	3 Months Ended							3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Mar. 31, 2014 GCP I	Dec. 31, 2013 GCP I	Mar. 31, 2014 GCP II	Dec. 31, 2013 GCP II	Mar. 31, 2014 Barrow Street	Mar. 31, 2013 Iridium
Fair Value, Measurement Inputs, Disclosure [Line Items]
Investment related to noncontrolling interests			$ 100,000	$ 100,000	$ 900,000	$ 900,000
Other commitment							300,000
Sale Of common stock (shares)								840
Share price (usd per share)								$ 6.69
Gain (Loss) on Investments	$ (5,231,000)	$ (2,081,000)