Basis of Presentation Basis of Presentation (Out-of-period-correction) (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017 USD ($)
Operating Income (Loss) [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Quantifying Misstatement in Current Year Financial Statements, Amount	$ 12
DAC [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Quantifying Misstatement in Current Year Financial Statements, Amount	8
Benefits, Claims, Losses and Settlement Expenses [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Quantifying Misstatement in Current Year Financial Statements, Amount	4
Income Tax Provision [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Quantifying Misstatement in Current Year Financial Statements, Amount	20
Other Comprehensive Income (Loss) [Member] | Decrease to other comprehensive income related to deferred taxes on currency translation adjustments [Member]
Quantifying Misstatement in Current Year Financial Statements [Line Items]
Quantifying Misstatement in Current Year Financial Statements, Amount	$ 87