Quarterly Results (Unaudited) - Schedule of Quarterly Financial Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Income Statement [Abstract]
Revenues	$ 1,493	$ 1,493	$ 1,539	$ 1,458	$ 1,506	$ 1,508	$ 1,562	$ 1,539	$ 5,983	$ 6,115	$ 6,321
Costs and expenses	1,251	1,283	1,302	1,264	1,306	1,265	1,312	1,307	5,100	5,190	5,409
Income (loss) from continuing operations	245	109	153	136	128	157	138	142	643	565	470
Net (income) loss from continuing operations attributable to noncontrolling interests							(1)	1	0	0	0
Income (loss) from continuing operations attributable to Starwood's common stockholders	245	109	153	136	128	157	137	143	643	565	470
Discontinued operations	(11)			1				70	(10)	70
Net income attributable to Starwood	$ 234	$ 109	$ 153	$ 137	$ 128	$ 157	$ 137	$ 213	$ 633	$ 635	$ 562
Basic -
Income (loss) from continuing operations	$ 1.41	$ 0.60	$ 0.81	$ 0.71	$ 0.68	$ 0.82	$ 0.72	$ 0.74	$ 3.49	$ 2.96	$ 2.44
Discontinued operations	$ (0.07)			$ 0.01				$ 0.37	$ (0.06)	$ 0.37	$ 0.48
Net income	$ 1.34	$ 0.60	$ 0.81	$ 0.72	$ 0.68	$ 0.82	$ 0.72	$ 1.11	$ 3.43	$ 3.33	$ 2.92
Diluted -
Income (loss) from continuing operations	$ 1.40	$ 0.59	$ 0.80	$ 0.71	$ 0.67	$ 0.81	$ 0.71	$ 0.73	$ 3.46	$ 2.92	$ 2.39
Discontinued operations	$ (0.07)			$ 0.01				$ 0.36	$ (0.06)	$ 0.36	$ 0.47
Net income	$ 1.33	$ 0.59	$ 0.80	$ 0.72	$ 0.67	$ 0.81	$ 0.71	$ 1.09	$ 3.40	$ 3.28	$ 2.86