Investments - Problem and Potential Problem Commercial Mortgage Loans (Details) - Mortgage Loans on Real Estate [Member] $ in Millions	12 Months Ended
	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Financing Receivable, Modifications [Line Items]
Maximum past due days that the mortgage loans are considered current	59 days
Debt service coverage ratio threshold, below which mortgage loans are considered potential problems	1.0
Loan-to-value ratio threshold, above which mortgage loans are considered potential problems	100.00%
Minimum past due days that mortgage loans are considered potential problems	30 days
Maximum past due days that mortgage loans are considered potential problems	60 days
Problem and potential problem mortgage loans	$ 139	$ 208
Loans modified but not considered troubled debt restructurings