Shareholders' Equity - Progression of the components of accumulated other comprehensive income (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Jan. 01, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance	$ 863
Other comprehensive income (loss), net of tax	416	$ 815	$ (544)
AOCI ending balance	1,273	863
Cumulative effect of accounting change	6,789	6,269	4,972		$ 5,331
Cumulative effect, period of adoption, adjustment
Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect of accounting change					4
Accumulated net investment gain (loss) including portion attributable to noncontrolling interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, Pretax	887	997	(689)
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, tax	(187)	(209)	145
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, net of tax	700	788	(544)
Reclassification from accumulated other comprehensive income, pretax	(389)	(11)	10
Reclassification from accumulated other comprehensive income, tax	82	2	(2)
Reclassification from accumulated other comprehensive income, net of tax	(307)	(9)	8
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax	498	986	(679)
Other comprehensive income (loss), tax	(105)	(207)	143
Other comprehensive income (loss), net of tax	393	779	(536)
Accumulated net investment gain (loss) attributable to noncontrolling interest
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, net of tax	0	0	0
Reclassification from accumulated other comprehensive income, net of tax	0	0	0
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax	0	0	0
Accumulated net investment gain (loss) attributable to parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, net of tax	700	788	(544)
Reclassification from accumulated other comprehensive income, net of tax	(307)	(9)	8
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance	862	83	840
Other comprehensive income (loss), net of tax	393	779	(536)
AOCI ending balance	1,255	862	83
Accumulated net investment gain (loss) attributable to parent | Cumulative effect, period of adoption, adjustment
Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect of accounting change	0	0		$ (221)
Accumulated net gain (loss) from cash flow hedges including portion attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax	30	36	2
Other comprehensive income (loss), tax	(6)	(8)	0
Other comprehensive income (loss), net of tax	24	28	2
Accumulated net gain (loss) from cash flow hedges attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax	0	0	0
Accumulated net gain (loss) from cash flow hedges attributable to parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance	17	(11)	(13)
Other comprehensive income (loss), net of tax	24	28	2
AOCI ending balance	41	17	(11)
Accumulated net gain (loss) from cash flow hedges attributable to parent | Cumulative effect, period of adoption, adjustment
Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect of accounting change	0	0		0
Accumulated foreign currency adjustment including portion attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax	(1)	7	(9)
Other comprehensive income (loss), tax	0	0	(1)
Other comprehensive income (loss), net of tax	(1)	7	(10)
Accumulated foreign currency adjustment attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax	(2)	0	0
Accumulated foreign currency adjustment attributable to parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance	(9)	(16)	(6)
Other comprehensive income (loss), net of tax	(3)	7	(10)
AOCI ending balance	(16)	(9)	(16)
Accumulated foreign currency adjustment attributable to parent | Neon Capital Limited
Accumulated Other Comprehensive Income [Roll Forward]
AOCI ending balance	(4)
Accumulated foreign currency adjustment attributable to parent | Cumulative effect, period of adoption, adjustment
Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect of accounting change		0		0
Accumulated defined benefit plans adjustment including portion attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax	0	1	0
Other comprehensive income (loss), tax	0	0	0
Other comprehensive income (loss), net of tax	0	1	0
Accumulated defined benefit plans adjustment attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax	0	0	0
Accumulated defined benefit plans adjustment attributable to parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance	(7)	(8)	(8)
Other comprehensive income (loss), net of tax	0	1	0
AOCI ending balance	(7)	(7)	(8)
Accumulated defined benefit plans adjustment attributable to parent | Cumulative effect, period of adoption, adjustment
Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect of accounting change	0	0		0
AOCI including portion attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax	527	1,030	(686)
Other comprehensive income (loss), tax	(111)	(215)	142
Other comprehensive income (loss), net of tax	416	815	(544)
AOCI attributable to noncontrolling interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), net of tax	(2)	0	0
AOCI attributable to parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance	863	48	813
Other comprehensive income (loss), net of tax	414	815	(544)
AOCI ending balance	1,273	863	48
Cumulative effect of accounting change	1,273	863	$ 48		813
AOCI attributable to parent | Neon Capital Limited
Accumulated Other Comprehensive Income [Roll Forward]
AOCI ending balance	$ (4)
AOCI attributable to parent | Cumulative effect, period of adoption, adjustment
Accumulated Other Comprehensive Income [Roll Forward]
Cumulative effect of accounting change		$ 0		$ (221)	$ (221)