Stockholders' Equity - Equity Attributable to Starwood's Stockholders (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	$ 3,235		$ 2,955
Net income (loss)	170	163	420	320
Equity compensation activity and other	31		132
Share repurchases	(79)		(140)
Other comprehensive income (loss)	21	(113)	11	(35)
Ending Balance	3,378		3,378
Common Shares [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	2		2
Net income (loss)
Equity compensation activity and other
Share repurchases
Other comprehensive income (loss)
Ending Balance	2		2
Additional Paid-in Capital [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	999		963
Net income (loss)
Equity compensation activity and other	31		128
Share repurchases	(79)		(140)
Other comprehensive income (loss)
Ending Balance	951		951
Accumulated Other Comprehensive Loss [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	(358)		(348)
Net income (loss)
Equity compensation activity and other
Share repurchases
Other comprehensive income (loss)	21		11
Ending Balance	(337)		(337)
Retained Earnings [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	2,587		2,337
Net income (loss)	170		420
Equity compensation activity and other
Share repurchases
Other comprehensive income (loss)
Ending Balance	2,757		2,757
Equity Attributable to Noncontrolling Interests [Member]
Schedule Of Stockholders Equity [Line Items]
Beginning Balance	5		1
Net income (loss)
Equity compensation activity and other			4
Share repurchases
Other comprehensive income (loss)
Ending Balance	$ 5		$ 5