Fair Value Measurements Hierarchy Table (Details) (Fair Value, Measurements, Recurring [Member], USD $)
In Thousands, unless otherwise specified
Dec. 31, 2012
Dec. 31, 2011
Level 1
   
Assets [Abstract]    
Total $ 240,280 $ 225,001
Liabilities [Abstract]    
Total 0 165
Level 2
   
Assets [Abstract]    
Total 128,605 32,672
Liabilities [Abstract]    
Total 24,769 23,800
Level 3
   
Assets [Abstract]    
Total 24,588 56,276
Liabilities [Abstract]    
Total 184 59,441
Total [Member]
   
Assets [Abstract]    
Total 393,473 313,949
Liabilities [Abstract]    
Total 24,953 83,406
Marketable Securities [Member] | Level 1
   
Assets [Abstract]    
Marketable securities 128,123 [1]  
Marketable Securities [Member] | Level 2
   
Assets [Abstract]    
Marketable securities 69,222 [1]  
Marketable Securities [Member] | Level 3
   
Assets [Abstract]    
Marketable securities 1,783 [1]  
Marketable Securities [Member] | Total [Member]
   
Assets [Abstract]    
Marketable securities 199,128 [1]  
Other Long-term Investments [Member] | Level 1
   
Assets [Abstract]    
Long-term investments 112,030 [1] 225,001 [1]
Other Long-term Investments [Member] | Level 2
   
Assets [Abstract]    
Long-term investments 59,383 [1] 32,672 [1]
Other Long-term Investments [Member] | Level 3
   
Assets [Abstract]    
Long-term investments 21,784 [1] 56,276 [1]
Other Long-term Investments [Member] | Total [Member]
   
Assets [Abstract]    
Long-term investments 193,197 [1] 313,949 [1]
Noncontrolling Interest | Level 1
   
Assets [Abstract]    
Non-controlling interests in certain funds 0 [2]  
Noncontrolling Interest | Level 2
   
Assets [Abstract]    
Non-controlling interests in certain funds 0 [2]  
Noncontrolling Interest | Level 3
   
Assets [Abstract]    
Non-controlling interests in certain funds 1,021 [2]  
Noncontrolling Interest | Total [Member]
   
Assets [Abstract]    
Non-controlling interests in certain funds 1,021 [2]  
Commodity contracts on precious metals [Member] | Level 1
   
Assets [Abstract]    
Commodity contracts on precious metals 127  
Liabilities [Abstract]    
Financial instruments 0 165
Commodity contracts on precious metals [Member] | Level 2
   
Assets [Abstract]    
Commodity contracts on precious metals 0  
Liabilities [Abstract]    
Financial instruments 27 64
Commodity contracts on precious metals [Member] | Level 3
   
Assets [Abstract]    
Commodity contracts on precious metals 0  
Liabilities [Abstract]    
Financial instruments 0 0
Commodity contracts on precious metals [Member] | Total [Member]
   
Assets [Abstract]    
Commodity contracts on precious metals 127  
Liabilities [Abstract]    
Financial instruments 27 229
Financial instruments [Member] | Level 1
   
Liabilities [Abstract]    
Financial instruments 0 0
Financial instruments [Member] | Level 2
   
Liabilities [Abstract]    
Financial instruments 24,742 23,736
Financial instruments [Member] | Level 3
   
Liabilities [Abstract]    
Financial instruments 0 0
Financial instruments [Member] | Total [Member]
   
Liabilities [Abstract]    
Financial instruments 24,742 23,736
Deferred Features of Subordinated Note [Member] | Level 1
   
Liabilities [Abstract]    
Deferred fee liability to related party   0
Deferred Features of Subordinated Note [Member] | Level 2
   
Liabilities [Abstract]    
Deferred fee liability to related party   0
Deferred Features of Subordinated Note [Member] | Level 3
   
Liabilities [Abstract]    
Deferred fee liability to related party   58,747
Deferred Features of Subordinated Note [Member] | Total [Member]
   
Liabilities [Abstract]    
Deferred fee liability to related party   58,747
Derivative features of subordinated notes [Member] | Level 1
   
Liabilities [Abstract]    
Derivative features of subordinated notes 0 0
Derivative features of subordinated notes [Member] | Level 2
   
Liabilities [Abstract]    
Derivative features of subordinated notes 0 0
Derivative features of subordinated notes [Member] | Level 3
   
Liabilities [Abstract]    
Derivative features of subordinated notes 184 694
Derivative features of subordinated notes [Member] | Total [Member]
   
Liabilities [Abstract]    
Derivative features of subordinated notes $ 184 $ 694
[1] For additional detail of the marketable securities and long-term investments see Note 5 - "Investments."
[2] Recorded within Other non-current assets.