Annual and transition report of foreign private issuers pursuant to Section 13 or 15(d)

Debt (Subordinated Debt Joint Venture Partners Narrative) (Details)

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Debt (Subordinated Debt Joint Venture Partners Narrative) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Debt Instrument [Line Items]    
Long-term Debt $ 27,716,999 $ 29,641,863
Subordinated Debt Joint Ventures Partners [Member]    
Debt Instrument [Line Items]    
Stated interest rate 0.00%  
Interest rate paid on unpaid interest 19.50%  
Subordinated Debt Joint Ventures Partners Before Amendment [Member]    
Debt Instrument [Line Items]    
Stated interest rate 20.00%  
Minimum [Member] | Subordinated Debt Joint Ventures Partners [Member]    
Debt Instrument [Line Items]    
Stated interest rate 15.00%  
Subordinated Debt [Member]    
Debt Instrument [Line Items]    
Long-term Debt $ 1,555,548 1,564,045
Subordinated Debt [Member] | Subordinated Debt Joint Ventures Partners [Member]    
Debt Instrument [Line Items]    
Long-term Debt $ 55,780 $ 64,280