(Loss) Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Details) (USD $) In Thousands, except Per Share data	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Net (loss) income attributable to Sotheby's	$ (29,719)	$ (19,361)	$ 99,936	$ 64,701
Weighted average common shares outstanding	67,410	66,377	67,263	66,238
Basic (loss) earnings per share - Sotheby's common shareholders	$ (0.44)	$ (0.29)	$ 1.47	$ 0.95
Denominator for calculation of diluted earnings per share	67,410	66,377	69,075	67,025
Diluted (loss) earnings per share - Sotheby's common shareholders	$ (0.44)	$ (0.29)	$ 1.43	$ 0.94
Basic [Member]
Net (loss) income attributable to Sotheby's	(29,719)	(19,361)	99,936	64,701
Less: Net income attributable to participating securities			1,169	1,575
Net (loss) income attributable to Sotheby's common shareholders	(29,719)	(19,361)	98,767	63,126
Weighted average common shares outstanding	67,410	66,377	67,263	66,238
Basic (loss) earnings per share - Sotheby's common shareholders	$ (0.44)	$ (0.29)	$ 1.47	$ 0.95
Diluted [Member]
Net (loss) income attributable to Sotheby's	(29,719)	(19,361)	99,936	64,701
Weighted average common shares outstanding	67,410	66,377	67,263	66,238
Less: Net income attributable to participating securities			1,142	1,560
Net (loss) income attributable to Sotheby's common shareholders	$ (29,719)	$ (19,361)	$ 98,794	$ 63,141
Weighted average dilutive potential common shares outstanding			1,812	787
Denominator for calculation of diluted earnings per share	67,410	66,377	69,075	67,025
Diluted (loss) earnings per share - Sotheby's common shareholders	$ (0.44)	$ (0.29)	$ 1.43	$ 0.94