Schedule II - Condensed Financial Information, Statements of Income (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Operating expenses:
Total operating expenses	$ 2,271	$ 2,289	$ 4,801	$ 4,610
Income before Income Taxes	1,134	813	2,024	1,632
Income tax expense (benefit)	324	310	621	615
Shareholders' Net Income	813	510	1,411	1,029
Shareholders' other comprehensive income (loss), net of tax:
Net unrealized appreciation (depreciation) on securities	67	177	74	350
Net unrealized appreciation (depreciation) on derivatives	0	(1)	(3)	(4)
Net translation of foreign currencies	27	(40)	139	41
Postretirement benefits liability adjustment	12	8	26	19
Shareholders' other comprehensive income (loss)	106	144	236	406
Shareholders' comprehensive income (loss)	$ 919	$ 654	$ 1,647	$ 1,435