Stockholders' Equity - Equity Attributable to Starwood's Stockholders (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	$ 1,299
Net income	90	$ 99
Equity compensation activity and other	(2)
Dividends	(63)
Other comprehensive income	23	$ (110)
Ending Balance	1,347
Common Shares [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	2
Ending Balance	2
Additional Paid-in Capital [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	115
Ending Balance	115
Accumulated Other Comprehensive Loss [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	(668)
Other comprehensive income	23
Ending Balance	(645)
Retained Earnings [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	1,847
Net income	90
Equity compensation activity and other	(2)
Dividends	(63)
Ending Balance	1,872
Equity Attributable to Noncontrolling Interests [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	3
Ending Balance	$ 3