Schedule II - Condensed Financial Information, Statements of Cash Flows (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Cash Flows from Operating Activities
Shareholders' net income	$ 772	$ 560	$ 2,493	$ 1,971
Adjustments to reconcile shareholders' net income to net cash provided by (used in) operating activities:
Other liabilities			113	221
Debt extinguishment costs	0	321	0	321
Other, net			(69)	33
Net cash provided by (used in) operating activities			3,644	3,511
Cash Flows from Investing Activities
Short term investments purchased			(660)	(722)
Other, net			(12)	0
Net cash provided by (used in) investing activities			(1,674)	(1,100)
Cash Flows from Financing Activities
Net change in short-term debt			(109)	(16)
Payments for debt extinguishment			0	(313)
Repayment of long-term debt			(131)	(1,250)
Net proceeds on issuance of long-term debt			19,884	1,584
Issuance of common stock			41	111
Repurchase of common stock			(310)	(1,961)
Other, net			(204)	(9)
Net cash provided by (used in) financing activities			19,115	(1,968)
Net increase (decrease) in cash and cash equivalents			21,060	471
Cash and cash equivalents, January 1,			2,972	3,185
Cash and cash equivalents, September 30,	$ 24,032	$ 3,656	$ 24,032	$ 3,656