Stockholders' Equity - Equity Attributable to Starwood's Stockholders (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	$ 1,528
Net income	99	137
Equity compensation activity and other	12
Dividends	(64)
Share Repurchases	(123)
Other comprehensive loss	(110)
Ending Balance	1,342
Common Shares [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance			2
Ending Balance	2		2
Additional Paid-in Capital [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	47
Equity compensation activity and other	12
Ending Balance	59
Accumulated Other Comprehensive Loss [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	(508)
Other comprehensive loss	(110)
Ending Balance	(618)
Retained Earnings [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	1,984
Net income	99
Dividends	(64)
Share Repurchases	(123)
Ending Balance	1,896
Equity Attributable to Noncontrolling Interests [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance			3
Ending Balance	$ 3		$ 3