Income Taxes - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Tax Reconciliation [Line Items]
Statutory rate of income taxes	35.00%	35.00%	35.00%	35.00%
Effective tax rate excluding the charge related to the exit of certain lines of business within subsidiaries		36.00%		35.00%
Other lines | Property and Casualty Insurance
Income Tax Reconciliation [Line Items]
Special charges related to the exit of certain lines of business within subsidiaries		$ 65
Other lines | Neon Capital Limited | Property and Casualty Insurance
Income Tax Reconciliation [Line Items]
Special charges related to the exit of certain lines of business within subsidiaries		$ 65