Schedule II - Condensed Statements Of Cash Flows (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities:
Investment income received	$ 118	$ 176	$ 205
Interest paid, net of interest converted to principal	(84)	(180)	(146)
Income taxes (paid) received	13	11	(1)
Net cash provided (used) by operating activities	(390)	(368)	(319)
Cash flows from investing activities:
Purchases of available-for-sale investments	(1,133)	(2,140)	(2,265)
Sales of available-for-sale investments	1,095	2,195	2,117
Paydowns and maturities of available-for-sale investments	724	857	329
Purchases of investments at fair value	(179)	(151)	(189)
Sales, paydowns and maturities of investments at fair value	198	617	212
Sales, paydowns and maturities (purchases) of short-term investments, net	143	(157)	420
(Payments) proceeds for derivative settlements	(16)	(98)	(24)
Net cash provided (used) by investing activities	1,738	1,267	1,206
Cash flows from financing activities:
Proceeds from investment agreements	12	15	12
Principal paydowns of investment agreements	(48)	(25)	(37)
Net cash provided (used) by financing activities	(1,265)	(1,096)	(752)
Effect of exchange rate changes on cash and cash equivalents	1	0	(1)
Net increase (decrease) in cash and cash equivalents	84	(197)	134
Cash and cash equivalents—beginning of year	83	280	146
Cash and cash equivalents—end of year	167	83	280
Reconciliation of net income (loss) to net cash provided (used) by operating activities: [Abstract]
Net income (loss)	(578)	(359)	(296)
Change in: [Abstract]
Net (gains) losses on financial instruments at fair value and foreign exchange	(70)	(157)	(8)
Deferred income tax provision (benefit)	12	13	0
Other operating	47	30	10
Total adjustments to net income (loss)	188	(9)	(23)
Net cash provided (used) by operating activities	(390)	(368)	(319)
Parent Company [Member]
Cash flows from operating activities:
Investment income received	101	156	132
Operating expenses paid	(47)	(17)	(17)
Interest paid, net of interest converted to principal	(60)	(88)	(91)
Income taxes (paid) received	5	34	(16)
Net cash provided (used) by operating activities	(1)	85	8
Cash flows from investing activities:
Purchases of available-for-sale investments	(216)	(278)	(495)
Sales of available-for-sale investments	183	319	175
Paydowns and maturities of available-for-sale investments	41	179	101
Purchases of investments at fair value	(2)	5	(9)
Sales, paydowns and maturities of investments at fair value	2	0	10
Sales, paydowns and maturities (purchases) of short-term investments, net	137	(61)	262
(Payments) proceeds for derivative settlements	(16)	(98)	(24)
Contributions (to) from subsidiaries, net	0	(14)	51
Advances (to) from subsidiaries, net	0	0	3
Net cash provided (used) by investing activities	129	52	74
Cash flows from financing activities:
Proceeds from investment agreements	12	15	11
Principal paydowns of investment agreements	(18)	(20)	(35)
Proceeds from long-term debt	0	0	40
Principal paydowns of long-term debt	(115)	(150)	0
Payments for affiliate loans	0	(19)	(71)
Restricted stock awards settlements	8	8	4
Net cash provided (used) by financing activities	(113)	(166)	(51)
Effect of exchange rate changes on cash and cash equivalents	0	0	(1)
Net increase (decrease) in cash and cash equivalents	15	(29)	30
Cash and cash equivalents—beginning of year	11	40	10
Cash and cash equivalents—end of year	26	11	40
Reconciliation of net income (loss) to net cash provided (used) by operating activities: [Abstract]
Net income (loss)	(578)	(359)	(296)
Change in: [Abstract]
Intercompany accounts receivable	(39)	(16)	(9)
Current income taxes	5	23	(15)
Equity in earnings of subsidiaries	450	333	283
Dividends from subsidiaries	81	134	112
Net (gains) losses on financial instruments at fair value and foreign exchange	67	57	(20)
Deferred income tax provision (benefit)	(4)	(88)	(35)
(Gains) losses on extinguishment of debt	0	1	(3)
Other operating	17	0	(9)
Total adjustments to net income (loss)	577	444	304
Net cash provided (used) by operating activities	$ (1)	$ 85	$ 8