Commitments and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2006 Hotel	Sep. 30, 2012 Hotel	Sep. 30, 2012 VIEs 16 [Member] Hotel	Sep. 30, 2012 VIEs 2 [Member]	Dec. 31, 2011 VIEs 2 [Member] Hotel	Dec. 31, 2011 VIEs 16 [Member] Hotel
Variable Interest Entity [Line Items]
Total number of hotels in which company has variable interest entity		21
Investments associated with VIEs			$ 96	$ 5	$ 5	$ 83
Loan Balance with VIEs			10			9
Number of hotels in which company has an investment			19		2	16
Possible cash outlay under contracts with performance guarantees				62
Loans to Owners		12
Unfunded loan commitments		18
Unfunded loan commitments expected to be funded in total		0
Unfunded loan commitments expected to be funded in year 1		0
Equity and other potential contributions associated with managed or joint venture properties		95
Equity and other potential contributions associated with managed or joint venture properties expected to be funded within one year		56
Surety bonds issued		$ 80
Number of hotels sold	33