Provision (Benefit) for Income Taxes - Reconciliations from Provision (Benefit) for Income Taxes from Continuing Operations at Federal Statutory Rate (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Effective Income Tax Rate Reconciliation, at Federal Statutory Income Tax Rate, Percent	21.00%	21.00%	35.00%
Provision (benefit) at statutory rate	$ 69	$ 66	$ (36)
Increases (decreases) in taxes resulting from:
State income taxes (net of federal benefit)	2	(8)	(12)
Valuation allowance on current year state income taxes (net of federal benefit)	14	17	17
Effective state income tax rate change (net of federal benefit)	(10)	(5)	(12)
Effective Income Tax Rate Reconciliation, Reversal of valuation allowance on federal capital loss	(10)	0	0
IncomeTaxReconciliationChangeInStatutoryTaxRate	0	0	(92)
Effective Income Tax Rate Reconciliation, Nondeductible Expense, Share-based Payment Arrangement, Amount	4	4	2
Other	1	0	5
Total provision (benefit)	$ 70	$ 74	$ (128)