Income Taxes - Effective Income Tax Rate Reconciliation (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Income Tax Disclosure [Abstract]
Statutory U.S. federal income tax (benefit) provision	$ (306)	$ 74	$ 105
State income taxes, net of U.S. federal tax benefit	1	2	3
Foreign income tax expense, net	19	13	2
Change in deferred tax asset valuation allowance	71	2
Tax rate change	(7)		(2)
REIT income not subject to tax	221	(69)	(92)
Derecognition and remeasurement of deferred taxes	(35)	13	7
Recognized built-in gain tax	29
Other	1
Total (benefit) provision for income taxes	$ (6)	$ 35	$ 23