Investments - Investment Revenues (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended	6 Months Ended
Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Principal Transaction Revenue [Line Items]
Net realized and unrealized gains (losses)			$ 1,217	$ 8,134
Interest income	277	345	453	709
Total investment revenues	3,624	2,170	1,767	11,604
Iridium [Member]
Principal Transaction Revenue [Line Items]
Net realized and unrealized gains (losses)	6,652	1,372	4,570	9,674
Merchant Banking Funds
Principal Transaction Revenue [Line Items]
Net realized and unrealized gains (losses)	(3,354)	388	(3,354)	1,092
Deferred gain on sale of certain merchant banking assets	$ 49	$ 65	$ 98	$ 129

This item represents the net total realized and unrealized gain (loss) included in earnings for the period as a result of selling or holding marketable securities categorized as trading, available-for-sale, or held-to-maturity, including the unrealized holding gain (loss) of held-to-maturity securities transferred to the trading security category and the cumulative unrealized gain (loss) which was included in other comprehensive income (a separate component of shareholders' equity) for available-for-sale securities transferred to trading securities during the period. Additionally, this item would include any gains (losses) realized during the period from the sale of investments accounted for under the cost method of accounting and losses recognized for other than temporary impairments (OTTI) of the subject investments.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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Reference 2: http://www.xbrl.org/2003/role/presentationRef

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Reference 4: http://www.xbrl.org/2003/role/presentationRef

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Reference 5: http://www.xbrl.org/2003/role/presentationRef

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