Consolidated Statements Of Shareholders' Equity (Parenthetical) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Net unrealized appreciation on investments, Change in year, income tax (expense) benefit	$ 152	$ (167)	$ 408
Cumulative translation adjustment, Change in year, income tax(expense) benefit	0	(12)	63
Pension liability adjustment, Change in year, income tax (expense) benefit	(6)	4	0
Net unrealized appreciation on investments
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	149	33	(88)
Reclassification out of Accumulated Other Comprehensive Income [Member] | Net unrealized appreciation on investments
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Tax	154	(176)	(391)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Tax	$ (2)	$ 9	$ 17