Accumulated Other Comprehensive Income (Loss) by Component Schedule of Accumulated Other Comprehensive Income (Loss) by Component (Details) - USD ($) $ in Millions		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2019	Dec. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	$ 12,244	$ 11,217	$ 12,244
Other comprehensive income (loss) before reclassifications		894	(922)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax		(35)	(28)
Other comprehensive income (loss) after tax (expense) benefit		929	(894)
Total stockholder's equity at end of period		12,215	11,217
Reclassification from AOCI, tax		10	8
Tax (expense) benefit on other comprehensive income (loss)		(240)	216
Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	32	(878)	32
Cumulative effect adjustments from changes in accounting guidance, net of tax	(16)
Total stockholder's equity at end of period	16	51	(878)
Net unrealized gains (losses) on investments with OTTI losses
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	25	16	25
Other comprehensive income (loss) before reclassifications		(13)	(7)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax		(12)	7
Other comprehensive income (loss) after tax (expense) benefit		(1)	(14)
Total stockholder's equity at end of period	30	15	16
Reclassification from AOCI, tax		3	(2)
Tax (expense) benefit on other comprehensive income (loss)		0	4
Net unrealized gains (losses) on other investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	750	61	750
Other comprehensive income (loss) before reclassifications		957	(801)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax		8	(3)
Other comprehensive income (loss) after tax (expense) benefit		949	(798)
Total stockholder's equity at end of period	859	1,010	61
Reclassification from AOCI, tax		(1)	2
Tax (expense) benefit on other comprehensive income (loss)		(255)	211
Pension and postretirement benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(645)	(775)	(645)
Other comprehensive income (loss) before reclassifications		(89)	(32)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax		(31)	(32)
Other comprehensive income (loss) after tax (expense) benefit		(58)	0
Total stockholder's equity at end of period	(775)	(833)	(775)
Reclassification from AOCI, tax		8	8
Tax (expense) benefit on other comprehensive income (loss)		15	1
Cumulative foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(98)	(180)	(98)
Other comprehensive income (loss) before reclassifications		39	(82)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax		0	0
Other comprehensive income (loss) after tax (expense) benefit		39	(82)
Total stockholder's equity at end of period	(98)	(141)	(180)
Reclassification from AOCI, tax		0	0
Tax (expense) benefit on other comprehensive income (loss)		$ 0	$ 0
ASU 2018-02 | Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting guidance, net of tax	12
ASU 2018-02 | Net unrealized gains (losses) on investments with OTTI losses
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting guidance, net of tax	5
ASU 2018-02 | Net unrealized gains (losses) on other investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting guidance, net of tax	137
ASU 2018-02 | Pension and postretirement benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting guidance, net of tax	(130)
ASU 2018-02 | Cumulative foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting guidance, net of tax	0
ASU 2016-01
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting guidance, tax	8
ASU 2016-01 | Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting guidance, net of tax	(28)
ASU 2016-01 | Net unrealized gains (losses) on investments with OTTI losses
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting guidance, net of tax	0
Cumulative effect adjustments from changes in accounting guidance, tax	0
ASU 2016-01 | Net unrealized gains (losses) on other investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting guidance, net of tax	(28)
Cumulative effect adjustments from changes in accounting guidance, tax	8
ASU 2016-01 | Pension and postretirement benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting guidance, net of tax	0
Cumulative effect adjustments from changes in accounting guidance, tax	0
ASU 2016-01 | Cumulative foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Cumulative effect adjustments from changes in accounting guidance, net of tax	0
Cumulative effect adjustments from changes in accounting guidance, tax	$ 0