Ownership Interests in and Advances to Partner Companies and Funds - Summarized Balance Sheets for Equity Method Investments (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Investments, Debt and Equity Securities [Abstract]
Current assets	$ 312,621	$ 221,001
Non-current assets	90,469	90,042
Total assets	403,090	311,043
Current liabilities	163,016	153,398
Non-current liabilities	80,050	75,324
Shareholders’ equity	160,024	82,321
Total liabilities and shareholders’ equity	$ 403,090	$ 311,043