Schedule II-Condensed Financial Information of Registrant (Statement of Comprehensive Income) (Details) - USD ($) $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Net income	$ 934	$ 1,183	$ 1,139	$ 1,551	$ 424	$ 960	$ 1,054	$ 1,312	$ 4,807	$ 3,750	$ 3,843
Other comprehensive income, net of tax:
Change in net unrealized gains/losses on investments									680	(418)	173
Change in non-credit component of other-than-ternporary impairment losses on investments									0	(2)	4
Change in net unrealized gains/losses on cash flow hedges									(16)	37	(65)
Change in net periodic pension and postretirement costs									26	(90)	51
Foreign currency translation adjustments									0	(1)	3
Other comprehensive income (loss)									690	(474)	166
Total comprehensive income									5,497	3,276	4,009
Parent Company [Member]
Net income									4,807	3,750	3,843
Other comprehensive income, net of tax:
Change in net unrealized gains/losses on investments									680	(418)	173
Change in non-credit component of other-than-ternporary impairment losses on investments									0	(2)	4
Change in net unrealized gains/losses on cash flow hedges									(16)	37	(65)
Change in net periodic pension and postretirement costs									26	(90)	51
Foreign currency translation adjustments									0	(1)	3
Other comprehensive income (loss)									690	(474)	166
Total comprehensive income									$ 5,497	$ 3,276	$ 4,009