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

Debt (ECAPS Subordinated Notes Narrative) (Details)

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Debt (ECAPS Subordinated Notes Narrative) (Details)
12 Months Ended
Dec. 31, 2015
USD ($)
Dec. 31, 2005
USD ($)
item
Dec. 31, 2014
USD ($)
Debt Instrument [Line Items]      
Long-term Debt $ 29,806,843,000   $ 30,402,392,000
Notes payable 29,806,843,000   30,402,392,000
Subordinated Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt 1,564,045,000   1,064,042,000
Notes payable 1,564,045,000   1,064,042,000
Subordinated Debt [Member] | ECAPs Subordinated Debt [Member]      
Debt Instrument [Line Items]      
Long-term Debt $ 1,000,000,000   1,000,000,000
Face amount   $ 1,000,000,000  
Debt, maturity 2065    
Number of tranches | item   2  
Notes payable $ 1,000,000,000   $ 1,000,000,000
Subordinated Debt [Member] | ECAPS Subordinated Debt $600 Million Tranche [Member]      
Debt Instrument [Line Items]      
Face amount 600,000,000    
Subordinated Debt [Member] | ECAPS Subordinated Debt $400 Million Tranche [Member]      
Debt Instrument [Line Items]      
Face amount $ 400,000,000    
Debt, fixed interest rate 6.25%    
Subordinated Debt [Member] | LIBOR [Member] | ECAPS Subordinated Debt $600 Million Tranche [Member]      
Debt Instrument [Line Items]      
Spread over reference rate 1.55%    
Subordinated Debt [Member] | LIBOR [Member] | ECAPS Subordinated Debt $400 Million Tranche [Member]      
Debt Instrument [Line Items]      
Spread over reference rate 1.80%