Accumulated Other Comprehensive Income (Loss) by Component (Schedule of accumulated other comprehensive income (loss) by component) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	$ 12,809
Other comprehensive income (loss) before reclassifications	(1,630)	$ (594)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	(7)	22
Other comprehensive income (loss) after tax (expense) benefit	(1,623)	(616)
Total stockholder's equity at end of period	10,817	12,089
Reclassification from AOCI, tax	3	(5)
Tax (expense) benefit on other comprehensive income (loss)	423	160
Accumulated other comprehensive income (loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	320	803
Total stockholder's equity at end of period	(1,303)	187
Net unrealized gains (losses) on investments with an allowance for credit losses
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period		0
Other comprehensive income (loss) before reclassifications		(3)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax		(3)
Other comprehensive income (loss) after tax (expense) benefit		0
Total stockholder's equity at end of period		0
Net unrealized gains (losses) on investments with an allowance for credit losses | Net unrealized gains (losses) on investments with an allowance for credit losses
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(2)
Other comprehensive income (loss) before reclassifications	(4)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	0
Other comprehensive income (loss) after tax (expense) benefit	(4)
Total stockholder's equity at end of period	(6)
Reclassification from AOCI, tax		1
Tax (expense) benefit on other comprehensive income (loss)		0
Net unrealized gains (losses) on investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period		1,745
Other comprehensive income (loss) before reclassifications		(593)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax		34
Other comprehensive income (loss) after tax (expense) benefit		(627)
Total stockholder's equity at end of period		1,118
Net unrealized gains (losses) on investments | Net unrealized gains (losses) on investments with an allowance for credit losses
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI, tax	0
Tax (expense) benefit on other comprehensive income (loss)	1
Net unrealized gains (losses) on investments | Net unrealized gains (losses) on other investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	1,039
Other comprehensive income (loss) before reclassifications	(1,612)
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	(1)
Other comprehensive income (loss) after tax (expense) benefit	(1,611)
Total stockholder's equity at end of period	(572)
Reclassification from AOCI, tax	1	(8)
Tax (expense) benefit on other comprehensive income (loss)	424	162
Pension and postretirement benefits
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(604)	(848)
Other comprehensive income (loss) before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	(6)	(9)
Other comprehensive income (loss) after tax (expense) benefit	6	9
Total stockholder's equity at end of period	(598)	(839)
Reclassification from AOCI, tax	2	2
Tax (expense) benefit on other comprehensive income (loss)	(2)	(2)
Cumulative foreign currency translation adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Total stockholder's equity at beginning of period	(113)	(94)
Other comprehensive income (loss) before reclassifications	(14)	2
Amounts reclassified from accumulated other comprehensive income (loss) net of tax	0	0
Other comprehensive income (loss) after tax (expense) benefit	(14)	2
Total stockholder's equity at end of period	(127)	(92)
Reclassification from AOCI, tax	0	0
Tax (expense) benefit on other comprehensive income (loss)	$ 0	$ 0