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

Debt (ECAPS subordinated notes) (Details)

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Debt (ECAPS subordinated notes) (Details) - Subordinated Debt [Member] - USD ($)
12 Months Ended
Dec. 31, 2015
Dec. 31, 2005
ECAPs Subordinated Debt [Member]    
Debt Instrument [Line Items]    
Face amount   $ 1,000,000,000.0
ECAPS Subordinated Debt $400 Million Tranche [Member]    
Debt Instrument [Line Items]    
Face amount $ 400,000,000.0  
Debt, fixed interest rate 6.25%  
ECAPS Subordinated Debt $600 Million Tranche [Member]    
Debt Instrument [Line Items]    
Face amount $ 600,000,000.0  
LIBOR [Member] | ECAPS Subordinated Debt $400 Million Tranche [Member]    
Debt Instrument [Line Items]    
Spread over reference rate 1.80%  
LIBOR [Member] | ECAPS Subordinated Debt $600 Million Tranche [Member]    
Debt Instrument [Line Items]    
Spread over reference rate 1.55%