Reinsurance (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Funds held under reinsurance agreements, liability	$ 3,200	$ 3,400
Reinsurance recoveries reported in insurance claims and policyholders' benefits reported on the Consolidated Statement of Operations	2,601	1,379	$ 1,450
Subsidiaries of Berkshire Hathaway Group [Member]
Largest Recoverables From Single Reinsurer	2,357
Gateway Rivers Insurance Company [Member]
Largest Recoverables From Single Reinsurer	284
Subsidiaries of Hartford Insurance Group [Member]
Largest Recoverables From Single Reinsurer	207
Significant Captive Program [Member]
Direct and ceded earned premiums	3,344	2,643	2,156
Reinsurance recoveries reported in insurance claims and policyholders' benefits reported on the Consolidated Statement of Operations	$ 2,282	$ 1,458	$ 712