Ownership Interests in and Advances to Partner Companies and Funds - Carrying Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Investments In And Advances To Affiliates [Line Items]
Equity method investments	$ 132,298	$ 154,666
Cost method investments	4,087	3,662
Advances to partner companies	25,240	25,142
Investments in and advance to affiliates, subsidiaries, associates, and joint ventures	161,625	183,470
Partner companies
Investments In And Advances To Affiliates [Line Items]
Equity method investments	131,852	154,219
Cost method investments	2,687	2,112
Private equity funds
Investments In And Advances To Affiliates [Line Items]
Equity method investments	446	447
Cost method investments	$ 1,400	$ 1,550