Leases (Schedule of Maturity Analysis of Operating and Finance Lease Liabilities) (Detail) - USD ($) $ in Millions	Dec. 31, 2020	Jan. 01, 2019
Operating Lease Liabilities, Payments Due [Abstract]
Maturity of operating lease liabilities, 2021	$ 4
Maturity of operating lease liabilities, 2022	3
Maturity of operating lease liabilities, 2023	2
Maturity of operating lease liabilities, 2024	2
Maturity of operating lease liabilities, 2025	1
Maturity of operating lease liabilities, after 2025	21
Maturity of operating lease liabilities, total undiscounted lease payments	33
Operating lease liabilities, present value adjustment	(12)
Present value of operating lease liabilities	21	$ 19
Finance Lease Liabilities, Payments, Due [Abstract]
Maturity of finance lease liabilities, 2021	7
Maturity of finance lease liabilities, 2022	6
Maturity of finance lease liabilities, 2023	4
Maturity of finance lease liabilities, 2024	3
Maturity of finance lease liabilities, 2025	2
Maturity of finance lease liabilities, after 2025	2
Maturity of finance lease liabilities, total undiscounted lease payments	24
Finance lease liabilities, present value adjustment	(3)
Present value of finance lease liabilities	$ 21