Shareholders' Equity - Progression of the components of accumulated other comprehensive income (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance			$ 863
Other comprehensive income, net of tax	$ 176	$ 109	368	$ 871
AOCI, other effects	1,233		863
AOCI ending balance	1,233		1,233
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	245	136	443	1,073
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, tax	(51)	(29)	(93)	(226)
Other comprehensive income (loss), unrealized holding gains on securities arising during the period, net of tax	194	107	350	847
Reclassification from accumulated other comprehensive income, pretax	(15)	1	0	(13)
Reclassification from accumulated other comprehensive income, tax	3	0	0	3
Reclassification from accumulated other comprehensive income, net of tax	(12)	1	0	(10)
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax	230	137	443	1,060
Other comprehensive income (loss), tax	(48)	(29)	(93)	(223)
Other comprehensive income, net of tax	182	108	350	837
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	0
Reclassification from accumulated other comprehensive income, net of tax	0	0	0	0
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income, net of tax	0	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	194	107	350	847
Reclassification from accumulated other comprehensive income, net of tax	(12)	1	0	(10)
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance	1,030	812	862	83
Other comprehensive income, net of tax	182	108	350	837
AOCI, other effects	1,212	920	862	83
AOCI ending balance	1,212	920	1,212	920
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	(7)	9	31	46
Other comprehensive income (loss), tax	1	(2)	(7)	(10)
Other comprehensive income, net of tax	(6)	7	24	36
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income, net of tax	0	0	0	0
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance	47	18	17	(11)
Other comprehensive income, net of tax	(6)	7	24	36
AOCI, other effects	41	25	17	(11)
AOCI ending balance	41	25	41	25
Accumulated Foreign Currency Adjustment Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax	0	(6)	(6)	(3)
Other comprehensive income (loss), tax	0	(1)	0	0
Other comprehensive income, net of tax	0	(7)	(6)	(3)
Accumulated Foreign Currency Adjustment Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income, net of tax	0	(1)	(2)	(2)
Accumulated Foreign Currency Adjustment Attributable to Parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance	(17)	(13)	(9)	(16)
Other comprehensive income, net of tax	0	(8)	(8)	(5)
AOCI, other effects	(13)	(21)	(13)	(21)
AOCI ending balance	(13)	(21)	(13)	(21)
Accumulated Foreign Currency Adjustment Attributable to Parent | Neon Capital Limited
Accumulated Other Comprehensive Income [Roll Forward]
AOCI, other effects	4		4
AOCI ending balance	4		4
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	1
Other comprehensive income (loss), tax	0	0	0	0
Other comprehensive income, net of tax	0	1	0	1
Accumulated Defined Benefit Plans Adjustment Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income, net of tax	0	0	0	0
Accumulated Defined Benefit Plans Adjustment Attributable to Parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance	(7)	(8)	(7)	(8)
Other comprehensive income, net of tax	0	1	0	1
AOCI, other effects	(7)	(7)	(7)	(7)
AOCI ending balance	(7)	(7)	(7)	(7)
AOCI Including Portion Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income (loss), pretax	223	141	468	1,104
Other comprehensive income (loss), tax	(47)	(32)	(100)	(233)
Other comprehensive income, net of tax	176	109	368	871
AOCI Attributable to Noncontrolling Interest
Accumulated Other Comprehensive Income [Roll Forward]
Other comprehensive income, net of tax	0	(1)	(2)	(2)
AOCI Attributable to Parent
Accumulated Other Comprehensive Income [Roll Forward]
AOCI beginning balance	1,053	809	863	48
Other comprehensive income, net of tax	176	108	366	869
AOCI, other effects	1,233	917	1,233	917
AOCI ending balance	1,233	$ 917	1,233	$ 917
AOCI Attributable to Parent | Neon Capital Limited
Accumulated Other Comprehensive Income [Roll Forward]
AOCI, other effects	4		4
AOCI ending balance	$ 4		$ 4