Stockholders' Equity - Equity Attributable to Starwood's Stockholders (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended				3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012	Mar. 31, 2013 Common Shares [Member]	Dec. 31, 2012 Common Shares [Member]	Mar. 31, 2013 Additional Paid-in Capital [Member]	Mar. 31, 2013 Accumulated Other Comprehensive Loss [Member]	Mar. 31, 2013 Retained Earnings [Member]	Mar. 31, 2013 Equity Attributable to Noncontrolling Interests [Member]
Beginning Balance	$ 3,142		$ 2	$ 2	$ 816	$ (338)	$ 2,657	$ 5
Net income (loss)	212	128					213	(1)
Equity compensation activity and other	52				52
Share repurchases	(48)				(48)
Other comprehensive income (loss)	(12)	39				(12)		(1)
Ending Balance	$ 3,345		$ 2	$ 2	$ 820	$ (350)	$ 2,870	$ 3