Schedule II - Condensed Financial Information, Statements of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Cash Flows from Operating Activities
Shareholders' net income	$ 588	$ 573	$ 1,121	$ 1,101
Adjustments to reconcile shareholders' net income to net cash provided by operating activities:
Other liabilities			216	78
Other, net			(50)	(41)
Net cash provided by / (used in) operating activities			1,109	1,002
Cash Flows from Investing Activities
Other, net			0	12
Net cash provided by/ (used in) investing activities			(96)	(832)
Cash Flows from Financing Activities
Net change in short-term debt			(10)	(96)
Net proceeds on issuance of long-term debt			894	0
Repayment of long-term debt			(938)	0
Issuance of common stock			128	80
Repurchase of common stock			(536)	(1,029)
Net cash provided by / (used in) financing activities			(446)	(1,007)
Net increase (decrease) in cash and cash equivalents			549	(828)
Cash and cash equivalents, January 1			1,420	2,795
Cash and cash equivalents, June 30	$ 1,969	$ 1,967	$ 1,969	$ 1,967