Fair Value Measurements - Fair Value of Certain Financial Instrument and Hierarchy Level Used to Estimate Fair Values (Detail) - USD ($) $ in Millions	Sep. 30, 2018	Dec. 31, 2017
SF CMBS Loan [Member] | Carrying amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loan	$ 725	$ 725
SF CMBS Loan [Member] | Fair Value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loan	705	721
HHV CMBS Loan [Member] | Carrying amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loan	1,275	1,275
HHV CMBS Loan [Member] | Fair Value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loan	1,219	1,256
Term Loan [Member] | Carrying amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loan	750	750
Term Loan [Member] | Fair Value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loan	751	749
Mortgage Loans [Member] | Carrying amount [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loan	207	207
Mortgage Loans [Member] | Fair Value [Member] | Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Loan	$ 199	$ 204