Reconciliation of Total Lease Payments, on Undiscounted Basis, to Lease Liability in Statement of Financial Position (Detail) $ in Millions	Mar. 31, 2019 USD ($)
Lessee Lease Description [Line Items]
Weighted-average discount rate - operating leases	5.40%
April 1, 2019 - December 31, 2019	$ 34
2020	44
2021	43
2022	40
2023	37
Thereafter	1,513
Total undiscounted cash flows	1,711
Long-term lease liabilities	625
Lease liabilities	625
Difference between undiscounted cash flows and discounted cash flows	$ 1,086
Ground Leases
Lessee Lease Description [Line Items]
Weighted-average discount rate - operating leases	5.40%
April 1, 2019 - December 31, 2019	$ 28
2020	37
2021	37
2022	37
2023	37
Thereafter	1,513
Total undiscounted cash flows	1,689
Long-term lease liabilities	604
Lease liabilities	604
Difference between undiscounted cash flows and discounted cash flows	$ 1,085
Office Leases and Other
Lessee Lease Description [Line Items]
Weighted-average discount rate - operating leases	4.00%
April 1, 2019 - December 31, 2019	$ 6
2020	7
2021	6
2022	3
Total undiscounted cash flows	22
Long-term lease liabilities	21
Lease liabilities	21
Difference between undiscounted cash flows and discounted cash flows	$ 1