Sotheby's (BID) 10-K 1 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Feb. 26, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	SOTHEBYS
Entity Central Index Key	823,094
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Document Type	10-K
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Amendment Flag	false
Entity Common Stock, Shares Outstanding		52,461,996
Entity Well-known Seasoned Issuer	Yes
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Public Float			$ 2,433,838,216

Consolidated Income Statements

Consolidated Income Statements - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues:
Agency commissions and fees	$ 741,580	$ 671,833	$ 791,920
Inventory sales	178,982	62,863	108,699
Finance	50,937	52,716	50,489
Other	17,890	17,965	10,386
Total revenues	989,389	805,377	961,494
Expenses:
Agency direct costs	82,142	73,324	91,919
Cost of inventory sales	181,487	81,782	111,090
Cost of finance revenues	19,312	17,738	15,780
Marketing	25,377	19,695	19,332
Salaries and related	313,895	307,659	302,825
General and administrative	172,950	161,356	159,148
Depreciation and amortization	24,053	21,817	19,481
CEO separation and transition costs (see Note 23)	0	0	4,232
Total expenses	819,054	682,761	759,773
Operating income	170,335	122,616	201,721
Interest income	1,184	1,294	1,776
Interest expense	(32,218)	(30,310)	(32,745)
Non-operating income (expense)	2,385	3,134	(1,453)
Income before taxes	141,686	96,734	169,299
Income tax expense	25,415	25,957	131,145
Equity in earnings of investees	2,508	3,262	5,327
Net income	118,779	74,039	43,481
Less: Net loss attributable to noncontrolling interest	(17)	(73)	(246)
Net income attributable to Sotheby's	$ 118,796	$ 74,112	$ 43,727
Basic earnings per share - Sotheby's common shareholders (usd per share)	$ 2.22	$ 1.28	$ 0.64
Diluted earnings per share - Sotheby's common shareholders (usd per share)	2.20	1.27	0.63
Cash dividends declared per common share (usd per share)	$ 0	$ 0	$ 0.4
Voluntary separation incentive programs
Expenses:
Restructuring charges, net	$ (162)	$ (610)	$ 36,938
2014 Restructuring plan
Expenses:
Restructuring charges, net	$ 0	$ 0	$ (972)

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Net income	$ 118,779	$ 74,039	$ 43,481
Other comprehensive income (loss):
Currency translation adjustments	13,889	(34,899)	(17,959)
Defined benefit pension plan	14,427	(6,515)	32,827
Total other comprehensive income (loss)	27,892	(24,154)	10,562
Comprehensive income (loss)	146,671	49,885	54,043
Less: Comprehensive (loss) income attributable to noncontrolling interest	(17)	(73)	(246)
Comprehensive income attributable to Sotheby's	146,688	49,958	54,289
Cash Flow Hedges
Other comprehensive income (loss):
Hedges	2,635	642	(4,306)
Net Investment Hedges
Other comprehensive income (loss):
Hedges	$ (3,059)	$ 16,618	$ 0

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 544,432	$ 496,031
Restricted cash (see Note 9)	361,578	59,106
Accounts receivable, net	795,239	433,614
Notes receivable, net	87,746	37,977
Inventory	74,483	159,043
Income tax receivables	6,601	6,475
Prepaid expenses and other current assets (see Note 12)	32,010	76,607
Total current assets	1,902,089	1,268,853
Notes receivable, net	507,538	651,159
Fixed assets, net	352,035	347,182
Goodwill	50,547	50,029
Intangible assets, net	11,492	13,393
Income tax receivables	324	686
Deferred income taxes	35,674	7,700
Other long-term assets (see Note 12)	227,608	165,424
Total assets	3,087,307	2,504,426
Current liabilities:
Client payables	996,197	511,876
Accounts payable and accrued liabilities	90,298	85,995
Accrued salaries and related costs	94,310	68,387
Current portion of long-term debt, net (see Note 9)	308,932	6,629
Accrued income taxes	8,127	26,912
Other current liabilities (see Note 11)	18,762	43,176
Total current liabilities	1,516,626	742,975
Credit facility borrowings	196,500	565,000
Long-term debt, net (see Note 9)	653,003	598,941
Accrued income taxes	37,651	16,600
Deferred income taxes	15,163	10,228
Other long-term liabilities (see Note 12)	51,424	65,080
Total liabilities	2,470,367	1,998,824
Commitments and contingencies (see Note 18)
Shareholders’ equity:
Common Stock, $0.01 par value, Authorized shares - 200,000,000, Issued shares - 70,378,873 and 70,054,948, Outstanding shares - 52,971,232 and 65,791,119	709	703
Additional paid-in capital	453,364	444,611
Treasury stock shares, at cost: 18,368,188 and 17,407,641	(554,551)	(509,885)
Retained earnings	779,699	660,347
Accumulated other comprehensive loss	(62,466)	(90,358)
Total shareholders’ equity	616,755	505,418
Noncontrolling interest	185	184
Total equity	616,940	505,602
Total liabilities and shareholders' equity	$ 3,087,307	$ 2,504,426

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	70,830,184	70,378,873
Common stock, shares outstanding	52,461,996	52,971,232
Treasury stock, shares	18,368,188	17,407,641

Consolidated Statements Of Cash

Consolidated Statements Of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities:
Net income attributable to Sotheby's	$ 118,796	$ 74,112	$ 43,727
Adjustments to reconcile net income attributable to Sotheby's to net cash provided by operating activities:
Depreciation and amortization	24,053	21,817	19,481
Gain from recognition of cumulative translation adjustment upon liquidation of foreign subsidiary	0	0	(105)
Deferred income tax (benefit) expense	(27,985)	(24,156)	81,689
Share-based payments	23,479	15,216	33,700
Net pension (benefit) cost	(4,660)	(6,895)	1,577
Inventory writedowns and bad debt provisions	14,902	23,441	21,729
Amortization of debt discount and issuance costs	1,690	1,619	3,072
Equity in earnings of investees	(2,508)	(3,262)	(5,327)
Other	1,077	794	45
Changes in assets and liabilities:
Accounts receivable	(297,690)	437,398	(14,190)
Client payables	451,186	(136,097)	(268,234)
Related party client payables (see Note 26)	0	(285,418)	285,418
Inventory (see Note 11)	73,709	29,746	(18,828)
Restricted cash related to interest on 2022 Senior Notes (see Note 9)	(4,375)	0	0
Changes in other operating assets and liabilities (see Note 13)	(5,489)	10,055	(27,632)
Net cash provided by operating activities	366,185	158,370	156,122
Investing Activities:
Funding of notes receivable	(198,481)	(321,127)	(334,989)
Collections of notes receivable	253,268	305,770	355,103
Capital expenditures	(20,694)	(21,363)	(11,338)
Acquisitions, net of cash acquired (see Notes 3 and 7)	(75)	(54,343)	0
Funding of investments	(6,542)	(2,200)	(30,725)
Distributions from investees	4,825	1,925	4,515
Proceeds from the sale of equity method investment	2,125	325	275
Settlement of net investment hedges (see Note 10)	29,110	(3,308)	0
(Increase) decrease in restricted cash	(3,276)	(26,097)	457
Net cash provided (used) by investing activities	60,260	(120,418)	(16,702)
Financing Activities:
Debt issuance and other borrowing costs	(5,729)	(320)	(9,642)
Proceeds from credit facility borrowings	181,500	164,500	186,500
Repayments of credit facility borrowings	(550,000)	(141,000)	(90,000)
Proceeds from refinancing of York Property Mortgage	0	0	325,000
Repayments of York Property Mortgage	(39,667)	(7,302)	(223,440)
Restricted cash related to York Property Mortgage (see Note 9)	1,527	(4,635)	0
Proceeds from the issuance of 2025 Senior Notes (see Note 9)	400,000	0	0
Restricted cash related to 2022 Senior Notes, principal and premium (see Note 9)	(307,875)	0	0
Repurchases of common stock	(44,495)	(359,885)	(125,000)
Dividends paid	(2,375)	(1,743)	(29,784)
Funding of employee tax obligations upon the vesting of share-based payments	(16,857)	(5,890)	(8,978)
Net cash (used) provided by financing activities	(383,971)	(356,275)	24,656
Effect of exchange rate changes on cash and cash equivalents	5,927	(34,343)	(9,208)
Increase (decrease) in cash and cash equivalents	48,401	(352,666)	154,868
Cash and cash equivalents at beginning of period	496,031	848,697	693,829
Cash and cash equivalents at end of period	$ 544,432	$ 496,031	$ 848,697

Consolidated Statements Of Chan

Consolidated Statements Of Changes in Shareholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Treasury Stock	Retained Earnings	Accumulated Other Comprehensive Loss
Balance at beginning of period at Dec. 31, 2014	$ 877,697	$ 695	$ 408,874	$ (25,000)	$ 569,894	$ (76,766)
Increase (Decrease) in Stockholders' Equity
Net income attributable to Sotheby's	43,727				43,727
Other comprehensive income (loss)	10,562					10,562
Common stock shares withheld to satisfy employee tax obligations	(8,978)		(8,978)
Restricted stock units vested, net	0	5	(5)
Amortization of share-based payment expense	33,700		33,700
Tax benefit from share-based payments	1,064		1,064
Shares and deferred stock units issued to directors	1,041		1,041
Repurchases of common stock	(125,000)			(125,000)
Cash dividends, $0.40 per common share	(27,107)				(27,107)
Cash dividend equivalents related to share-based payments	(279)				(279)
Balance at end of period at Dec. 31, 2015	806,427	700	435,696	(150,000)	586,235	(66,204)
Increase (Decrease) in Stockholders' Equity
Net income attributable to Sotheby's	74,112				74,112
Other comprehensive income (loss)	(24,154)					(24,154)
Common stock shares withheld to satisfy employee tax obligations	(5,890)		(5,890)
Restricted stock units vested, net	0	3	(3)
Amortization of share-based payment expense	15,216		15,216
Tax deficiency from share-based payments	(1,342)		(1,342)
Shares and deferred stock units issued to directors	934		934
Repurchases of common stock	(359,885)			(359,885)
Balance at end of period at Dec. 31, 2016	505,418	703	444,611	(509,885)	660,347	(90,358)
Increase (Decrease) in Stockholders' Equity
Net income attributable to Sotheby's	118,796				118,796
Other comprehensive income (loss)	27,892					27,892
Stock options exercised	1,107	1	1,106
Common stock shares withheld to satisfy employee tax obligations	(16,857)		(16,857)
Restricted stock units vested, net	0	5	(5)
Amortization of share-based payment expense	23,479		23,479
Tax benefit from share-based payments	2,700
Shares and deferred stock units issued to directors	999		999
Repurchases of common stock	(44,495)			(44,495)
Other adjustments related to share-based payments	416		31	(171)	556
Balance at end of period at Dec. 31, 2017	$ 616,755	$ 709	$ 453,364	$ (554,551)	$ 779,699	$ (62,466)

Consolidated Statements Of Cha8

Consolidated Statements Of Changes in Shareholders’ Equity (Parenthetical) - $ / shares	Jan. 21, 2016	Dec. 31, 2015
Statement of Stockholders' Equity [Abstract]
Dividends declared (usd per share)	$ 0.10	$ 0.40

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation —The Consolidated Financial Statements included herein have been prepared in accordance with accounting principles generally accepted in the United States of America ("U.S. GAAP") and pursuant to the rules and regulations of the SEC. In the Consolidated Financial Statements, unless otherwise stated, the terms "art," "works of art," "artwork," and "property" may, as appropriate, refer to authenticated fine art, decorative art, jewelry, wine, or collectibles. Principles of Consolidation —The Consolidated Financial Statements include the accounts of our wholly-owned subsidiaries and Sotheby's (Beijing) Auction Co., Ltd. ("Sotheby's Beijing"), a joint venture in which we have a controlling 80% ownership interest. The net loss attributable to the minority owner of Sotheby's Beijing is reported as "Net Loss Attributable to Noncontrolling Interest" in our Consolidated Income Statements and the non-controlling 20% ownership interest is reported as "Noncontrolling Interest" within the Equity section of our Consolidated Balance Sheets. Intercompany transactions and balances among our subsidiaries are eliminated in consolidation. Equity investments through which we may significantly influence, but not control, the investee, are accounted for using the equity method. Under the equity method, our share of investee earnings or losses is recorded in our Consolidated Income Statements within Equity in Earnings of Investees. Our interest in the net assets of these investees is recorded on our Consolidated Balance Sheets within Equity Method Investments. See Note 5 for information related to our equity method investments. Foreign Currency Translation —Assets and liabilities recorded in foreign currencies are translated at the exchange rate on the balance sheet date. Revenues, expenses, gains, and losses recorded in foreign currencies are translated using the monthly average exchange rates prevailing during the period in which they are recognized. Translation adjustments resulting from this process are recorded to Other Comprehensive Income (Loss) and reported on our Consolidated Balance Sheets within Accumulated Other Comprehensive Loss until the subsidiary is sold or liquidated, at which point the adjustments are recognized in Net Income. Adjustments to Prior Period Presentation —In March 2016, the Financial Accounting Standards Board (the "FASB") issued Accounting Standards Update ("ASU") 2016-09, Compensation-Stock Compensation: Improvements to Employee Share-Based Payment Accounting. ASU 2016-09 simplifies several aspects of the accounting for and presentation of share-based payment transactions, including the accounting for the related income tax consequences and certain classifications within the statement of cash flows. We adopted ASU 2016-09 on its effective date of January 1, 2017. ASU 2016-09 requires that all excess tax benefits and deficiencies resulting from the vesting of share-based payments be recorded in the income statement, whereas previous guidance generally permitted such items to be recorded in the equity section of the balance sheet provided that an adequate level of previously recorded excess tax benefits existed. We adopted this aspect of ASU 2016-09 on a prospective basis. The adoption of ASU 2016-09 and the vesting of certain share-based payments in 2017 resulted in the recording of a $2.7 million income tax benefit in our Consolidated Income Statements for the year ended December 31, 2017, which decreased our effective income tax rate by approximately 1.8% . Under previous guidance, this income tax benefit would have been recorded as an increase to Additional Paid-In Capital on our Consolidated Balance Sheets. ASU 2016-09 also changed how excess tax benefits resulting from the vesting of share-based payments are presented in the statement of cash flows. ASU 2016-09 requires that such excess tax benefits be classified within Operating Activities along with other income tax cash flows. Under previous guidance, excess tax benefits resulting from the vesting of share-based payments were presented as a cash inflow within Financing Activities and a corresponding cash outflow within Operating Activities. We adopted this aspect of ASU 2016-09 on a retrospective basis. The adoption of ASU 2016-09 and the vesting of certain share-based payments in 2017 resulted in the classification of $2.7 million of excess tax benefits within Operating Activities in our Consolidated Statement of Cash Flows for the year ended December 31, 2017. The retrospective adoption of ASU 2016-09 did not have an effect on our Consolidated Statement of Cash Flows for the year ended December 31, 2016 because no excess tax benefits were recorded in that period. The following table summarizes the effect of retrospectively adopting ASU 2016-09 on our Statement of Cash Flows for the year ended December 31, 2015 (in thousands of dollars): Year Ended December 31, 2015 As Previously Reported ASU 2016-09 Adjustments As Adjusted Operating Activities: Adjustments to reconcile net income attributable to Sotheby's to net cash provided by operating activities: Excess tax benefits from share-based payments $ (1,064 ) $ 1,064 $ — Net cash provided by operating activities $ 155,058 $ 1,064 $ 156,122 Financing Activities: Excess tax benefits from share-based payments $ 1,064 $ (1,064 ) $ — Net cash provided by financing activities $ 25,720 $ (1,064 ) $ 24,656 The adoption of the other aspects of ASU 2016-09 did not have a material impact on our Consolidated Financial Statements as of and for years ended December 31, 2017 and 2016. Restricted Cash —Restricted cash may include legally restricted deposits or amounts, cash balances restricted as a result of contracts entered into with third parties or Company statements of intention with regard to particular cash deposits. As of December 31, 2017 and 2016, our Restricted Cash balances include the following (in thousands of dollars): December 31, 2017 2016 Funds deposited with the trustee for the redemption of the 2022 Senior Notes (see Note 9) $ 312,250 $ — Consignor funds held in legally segregated accounts 46,029 53,811 Cash Management Account related to the York Property Mortgage (see Note 9) 3,107 4,635 Other 192 660 Total Restricted Cash $ 361,578 $ 59,106 Valuation of Inventory and Loan Collateral —The art market is not a highly liquid trading market. As a result, the valuation of art is inherently subjective and the realizable value of art often fluctuates over time. In estimating the realizable value of art held in inventory and art pledged as collateral for client loans, we consider the following complex array of factors: (i) whether the property is expected to be offered at auction or sold privately, and the timing of any such sale; (ii) the supply and demand for the property, taking into account current art market conditions, as well as changing trends as to which collecting categories and artists are most sought after; (iii) recent sale prices achieved for comparable items within a particular collecting category and/or by a particular artist; (iv) the state of the global economy and financial markets; and (v) our intent and ability to hold the property in order to maximize its realizable value. Due to the inherent subjectivity involved in estimating the realizable value of art held in inventory and art pledged as collateral for client loans, our estimates of realizable value may prove, with the benefit of hindsight, to be different than the amount ultimately realized upon sale. See below for further discussion of our accounting policies related to Notes Receivable and Inventory. Accounts Receivable and Allowance for Doubtful Accounts —Accounts Receivable principally includes amounts due from buyers as a result of auction and private sale transactions. The recorded amount reflects the purchase price of the property, including any commissions, as well as any applicable taxes and royalties. The Allowance for Doubtful Accounts principally includes estimated losses associated with situations when we have paid the net sale proceeds to the seller and it is probable that payment will not be collected from the buyer. The Allowance for Doubtful Accounts also includes an estimate of probable losses inherent in the remainder of the Accounts Receivable balance. The amount of the required allowance is based on the facts available to management, including the value of any property held as collateral, and is reevaluated and adjusted as additional facts become known. Based on all available information, we believe that the Allowance for Doubtful Accounts is adequate as of December 31, 2017 ; however, actual losses may ultimately exceed the recorded allowance. As of December 31, 2017 and 2016 , the Allowance for Doubtful Accounts was $8.7 million and $7.7 million , respectively. See Note 4 for information related to Accounts Receivable. Notes Receivable and Allowance for Credit Losses —Notes Receivable includes loans made to clients that are secured by artworks. The classification of a loan as current or non-current on our Consolidated Balance Sheets takes into account the contractual maturity date of the loan, as well as the likelihood of renewing the loan on or before its contractual maturity date. The determination of whether a specific loan is impaired and the amount of any required allowance is based on the facts available to management and is reevaluated and adjusted as additional facts become known. A loan is considered to be impaired when we determine that it is probable that a portion of the principal and interest owed by the borrower will not be recovered after taking into account the estimated realizable value of the collateral securing the loan, as well as the ability of the borrower to repay any shortfall between the value of the collateral and the amount of the loan. An allowance is also established for probable losses inherent in the remainder of the loan portfolio based on historical data related to loan losses. See Note 4 for information related to Notes Receivable. Inventory —Inventory consists of artworks that we own and includes the following general categories: (i) items that have been obtained as a result of the failure of guaranteed property to sell at auction , (ii) items that have been purchased opportunistically, including property acquired for sale at auction, and (iii) other objects obtained incidental to the auction process (e.g., as a result of buyer default). See Note 19 for information related to auction guarantees. Inventory is valued on a specific identification basis at the lower of cost or our estimate of realizable value (i.e., the expected sale price upon disposition). If there is evidence that the estimated realizable value of a specific item held in Inventory is less than its carrying value, a writedown is recorded to reflect our revised estimate of realizable va lue. For the years ended December 31, 2017 , 2016 , and 2015 , inventory writedowns totaled $13.6 million , $22.3 million , and $20.1 million , respectively, and were recorded within Cost of Inventory Sales in our Consolidated Income Statements. Although all of the items held in Inventory are available for immediate sale, the timing of eventual sale is difficult to predict due to the high value and unique nature of each item, as well as the cyclical nature of the global art market. We expect that the items held in Inventory will be sold in the ordinary course of our business during the normal operating cycle for such items. Fixed Assets —Fixed Assets are stated at cost less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method over the estimated useful life of the asset. Buildings are depreciated over a useful life of up to 50 years . Building improvements are depreciated over a useful life of up to 20 years . Furniture and fixtures are depreciated over a useful life of up to seven years. Leasehold improvements are amortized using the straight-line method over the lesser of the term of the related lease or the estimated useful life of the improvement. Computer software purchased or developed for internal use consists of the cost of purchased software, as well as direct external and internal software development costs. These costs are amortized on a straight-line basis over the estimated useful life of the software, which is typically between seven to ten years for enterprise systems and three years for other types of software. See Note 6 for information related to Fixed Assets. Goodwill —Goodwill represents the excess of the purchase price paid over the fair value of net assets acquired in a business combination. Goodwill is not amortized, but is tested annually for impairment at the reporting unit level as of October 31 and between annual tests if indicators of potential impairment exist. These indicators could include a decline in our stock price and market capitalization, a significant change in the outlook for the reporting unit's business, lower than expected operating results, increased competition, legal factors, or the sale or disposition of a significant portion of a reporting unit. An impairment loss is recognized for any amount by which the carrying value of a reporting unit's goodwill exceeds its fair value. The fair value of the reporting units in our Agency segment is determined in reference to a blend of the income and market approaches, and the fair value of our art advisory reporting unit is determined using a discounted cash flow methodology. See Note 7 for information related to Goodwill. The significant assumptions used in the income approach and discounted cash flow approach include (i) forecasted growth rates and (ii) forecasted profitability, both of which are estimated based on consideration of our historical performance and projections of our future performance, and (iii) discount rates that are used to calculate the value of future projected cash flows, which rates are derived based on our estimated weighted average cost of capital. The significant assumptions used in the market approach include selected multiples applied to certain operating metrics. Considerable judgment is necessary to evaluate the impact of operating changes and business initiatives in order to estimate future growth rates and profitability in order to estimate future cash flows and multiples. This is particularly true in a cyclical business, like that of Sotheby's. Future business results could significantly impact the evaluation of our goodwill which could have a material impact on the determination of whether a potential impairment exists and the size of any such impairment. Intangible Assets —Intangible assets are amortized over their estimated useful lives unless the useful life of a particular intangible asset is deemed to be indefinite. If indicators of potential impairment exist, intangible assets with defined useful lives are tested for impairment based on our estimates of undiscounted cash flows and, if impaired, written down to fair value based on either discounted cash flows or appraised values. See Note 7 for information related to Intangible Assets. Impairment of Long-Lived Assets —Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. In such situations, long-lived assets are considered impaired when estimated future cash flows (undiscounted and without interest charges) resulting from the use of the asset and its eventual disposition are less than the asset's carrying amount. In such situations, the asset is written down to the present value of the estimated future cash flows. Factors that are considered when evaluating long-lived assets for impairment include a current expectation that it is more likely than not that the long-lived asset will be sold significantly before the end of its useful life, a significant decrease in the market price of the long-lived asset, and a significant change in the extent or manner in which the long-lived asset is being used. Deferred Tax Assets & Liabilities —We follow the liability method of accounting for income taxes under which deferred tax assets and liabilities are recognized, based on enacted tax rates, for the future tax consequences of (i) temporary differences between the tax basis of assets and liabilities and their reported amounts in our consolidated financial statements and (ii) operating loss and tax credit carry-forwards for tax purposes. A valuation allowance is recorded to reduce our deferred tax assets to the amount that is more likely than not to be realized. In assessing the need for the valuation allowance, management considers, among other things, projections of future taxable income and ongoing prudent and feasible tax planning strategies. If we determine that sufficient negative evidence exists (for example, if we experience cumulative three-year losses in a certain jurisdiction), then we will consider recording a valuation allowance against a portion or all of the deferred tax assets in that jurisdiction. If, after recording a valuation allowance, our projections of future taxable income and other positive evidence considered in evaluating the need for a valuation allowance prove, with the benefit of hindsight, to be inaccurate, it could prove to be more difficult to support the realization of our deferred tax assets. As a result, an additional valuation allowance could be required, which would have an adverse impact on our effective income tax rate and results. Conversely, if, after recording a valuation allowance, we determine that sufficient positive evidence exists in the jurisdiction in which the valuation allowance was recorded (for example, if we are no longer in a three-year cumulative loss position in the jurisdiction, and we expect to have future taxable income in that jurisdiction based upon our forecasts and the expected timing of deferred tax asset reversals), we may reverse a portion or all of the valuation allowance in that jurisdiction. In such situations, the adjustment made to the deferred tax asset would have a favorable impact on our effective income tax rate and results in the period such determination was made. See Note 16 for information related to income taxes, including the recorded balances of our valuation allowance related to deferred tax assets. On December 22, 2017, the U.S. Tax Cuts and Jobs Act (the "Act") was enacted into law. Among other things, the Act reduces the U.S. corporate income tax rate from 35% to 21% , and makes changes to certain other business-related exclusions, deductions and credits. The SEC soon thereafter issued Staff Accounting Bulletin No. 118 ("SAB 118"), which allows companies to record the income tax effects of the Act as a provisional amount based upon reasonable estimates. As of December 31, 2017, we have not completed our accounting for the income tax effects of the Act. However, in accordance with SAB 118, we recorded a provisional net income tax expense of approximately $1.2 million in the fourth quarter of 2017 based on reasonable estimates for those tax effects. This provisional net income tax expense is subject to adjustments as we complete our analysis of the Act, collect and prepare the necessary data, and interpret any additional guidance issued by the U.S. Treasury Department, IRS, the FASB, and other standard-setting and regulatory bodies. Adjustments may impact our provision for income taxes and effective tax rate in the period in which the adjustments are made. Our accounting for the income tax effects of the Act will be completed during the measurement period, which should not extend beyond one year from the enactment date. The impact of the provisional accounting effects of the Act are described in greater detail in Note 16. Auction Guarantees —From time-to-time in the ordinary course of our business, we will guarantee to a consignor a minimum sale price in connection with the sale of property at auction (an "auction guarantee"). If the property offered under the auction guarantee sells above the minimum guaranteed price, we are generally entitled to a share of the excess proceeds (the "overage"). In the event that the property sells for less than the minimum guaranteed price, we must perform under the auction guarantee by funding the difference between the sale price at auction and the amount of the auction guarantee (the "shortfall"). The amount of any shortfall recorded in our Consolidated Income Statements is reduced by any auction commissions earned on property sold under the auction guarantee. If any item of property offered under the auction guarantee does not sell, the amount of the auction guarantee must be paid, but we then take ownership of the unsold property and may recover the amount paid through its future sale. In certain limited situations, if the guaranteed property fails to sell at auction or if the purchaser defaults, the consignor has the right to cancel the auction guarantee and retain the property. In situations when an item of guaranteed property does not sell and we take ownership of the property, it is recorded as Inventory on our Consolidated Balance Sheets at the lower of its cost (i.e., the amount paid under the auction guarantee) or our estimate of the property's net realizable value (i.e., the expected sale price upon its eventual disposition). The market for fine art, decorative art, and jewelry is not a highly liquid trading market. As a result, the valuation of property acquired as a result of failed auction guarantees is inherently subjective and its realizable value often fluctuates over time. Accordingly, the proceeds ultimately realized on the sale of previously guaranteed property may equal, exceed, or be less than the estimated net realizable value recorded as Inventory on our Consolidated Balance Sheets. The estimated fair value of our obligation to perform under our auction guarantees is recorded on our Consolidated Balance Sheets within Accounts Payable and Accrued Liabilities. This estimated fair value is based on an analysis of historical loss experience related to auction guarantees and does not include the impact of risk-sharing arrangements that may have mitigated all or a portion of any historical losses. See Note 19 for information related to auction guarantees and any associated risk-sharing arrangements. Financial Instruments —Our material financial instruments include (i) Cash and Cash Equivalents; (ii) Restricted Cash; (iii) Notes Receivable; (iv) credit facility borrowings; (v) the mortgage on our headquarters building in New York; (vi) various derivative financial instruments; and (vii) unsecured senior notes. The carrying amounts of Cash and Cash Equivalents, Restricted Cash, Notes Receivable, the mortgage on our headquarters building in New York, and credit facility borrowings do not materially differ from their estimated fair values due to their nature and the variable interest rates associated with each of these financial instruments. See Note 9 for fair value information related to our unsecured senior notes and Note 10 for fair value information related to derivative financial instruments. Revenue Recognition (Agency Commissions and Fees) —Through our Agency segment, we accept property on consignment, stimulate buyer interest through professional marketing techniques, and match sellers (also known as consignors) to buyers through the auction or private sale process. Prior to offering a work of art for sale, we perform due diligence activities to authenticate and determine the ownership history of the property being sold. The revenue recognition policy for each of the principal components of Agency Commissions and Fees is described below. (1) Auction Commission Revenues —In our role as auctioneer, we accept property on consignment and match sellers to buyers through the auction process. As compensation for our auction services, we earn a commission from both the buyer ("buyer's premium") and, to a lesser extent, the seller ("seller's commission") (collectively, "auction commission revenue"), both of which are calculated as a percentage of the hammer price of the property sold at auction. On the fall of the auctioneer's hammer, the highest bidder becomes legally obligated to pay the full purchase price, which includes the hammer price of the property purchased plus the buyer's premium, and the seller is legally obligated to relinquish the property in exchange for the hammer price less any seller's commissions. Auction commission revenue is recognized on the date of the auction sale upon the fall of the auctioneer's hammer, which is the point in time when we have substantially accomplished what we must do to be entitled to the benefits represented by the auction commission revenue. Subsequent to the date of the auction sale, our remaining obligations for our auction services relate only to the collection of the purchase price from the buyer and the remittance of the net sale proceeds to the seller. These remaining service obligations are not an essential part of our auction services. Under the standard terms and conditions of our auction sales, we are not obligated to pay the consignor for property that has not been paid for by the buyer. If a buyer defaults on payment, the sale is cancelled, and the property is returned to the consignor. We continually evaluate the collectability of amounts due from individual buyers and only recognize auction commission revenue when the collection of the amount due from the buyer is reasonably assured. If we determine that it is probable that the buyer will default, a cancelled sale is recorded in the period in which that determination is made and the associated Accounts Receivable balance, including our auction commission, is reversed. Our judgments regarding the collectability of Accounts Receivable are based on an assessment of the buyer's payment history, discussions with the buyer, and the value of any property held as security against the buyer's payment obligation. Our judgments with respect to the collectability of amounts due from buyers for auction purchases may prove, with the benefit of hindsight, to be incorrect. Historically, cancelled sales have not been material in relation to the aggregate hammer price of property sold at auction. Auction commission revenues are recorded net of commissions owed to third parties, which are principally the result of situations when the buyer's premium is shared with the consignor or with the counterparty in an auction guarantee risk and reward sharing arrangement (see Note 19 ). Additionally, in certain situations, auction commissions are shared with third parties who introduce us to auction consignors or otherwise facilitate the sale of property at auction. See Note 27, which discusses a change in the presentation of these amounts that will become effective on January 1, 2018 as a the result of the adoption of a new accounting standard related to revenue recognition. (2) Private Sale Commission Revenues —Private sale commission revenues are earned through the direct brokering of purchases and sales of art. Similar to auction sales, the primary service that we provide in a private sale transaction is the matching of the seller to a buyer in a legally binding transaction. Private sales are initiated either by a client wishing to sell property with Sotheby's acting as its exclusive agent in the transaction or a prospective buyer who is interested in purchasing a certain work of art privately. Such arrangements are evidenced by a legally binding agreement between Sotheby's and the seller (a "Seller Agreement"), which outlines the terms of the arrangement, including the desired sale price and the amount or rate of commission to be earned. In certain situations, we may also execute a legally binding agreement with the buyer stipulating the terms of the transaction (a "Buyer Agreement"). The timing of revenue recognition for private sale commissions is evaluated on a case-by-case basis, and in large part, is dependent upon whether a Buyer Agreement has been executed. Additionally, a careful analysis of the individual facts and circumstances is performed for each transaction to fully understand our obligations and performance requirements related to the transaction. In transactions with a Buyer Agreement, our services are performed on the date that the Buyer Agreement is executed. At this point, any remaining service obligations are considered to be inconsequential and perfunctory. Such remaining service obligations normally relate only to the collection of the purchase price from the buyer and the remittance of the net sale proceeds to the seller. These remaining service obligations are not an essential part of the services that we provide in a private sale transaction. In the absence of an executed Buyer Agreement, revenue recognition is deferred until we have performed our substantive service obligations in the transaction and the buyer has paid the full purchase price thereby evidencing the terms of the arrangement. Private sale commission revenues are recorded net of commissions owed to third parties. In certain situations, commissions are shared with third parties who introduce us to consignors who sell property through a private sale transaction. See Note 27, which discusses a change in the presentation of these amounts that will become effective on January 1, 2018 as a the result of the adoption of a new accounting standard related to revenue recognition. (3) Other Agency Commissions and Fees (Net) —Included in Other Agency Commissions and Fees is our share of overage or shortfall related to guaranteed property offered or sold at auction. The overage or shortfall related to guaranteed property is generally recognized in the period in which the property is offered at auction. However, a shortfall is recognized prior to the date of the auction if we determine that a loss related to an auction guarantee is probable. In such situations, we estimate the amount of the loss based on the difference between the amount of the auction guarantee and the expected selling price of the property, including buyer's premium. Also included in Other Agency Commissions and Fees (Net) are commissions and fees earned on sales of art brokered by third parties, fees charged to consignors for property withdrawn prior to auction, and catalogue subscription and advertising revenues. These revenues are recognized in our Consolidated Income Statements when the underlying event occurs or over the period during which we provide the service to our customer. Revenue Recognition (Inventory Sales) —Inventory sales are recognized in the period in which the sale is completed, title to the property passes to the purchaser, and we have fulfilled any other obligations that may be relevant to the transaction, including, but not limited to, delivery of the property. In instances when Inventory is sold at auction, the associated buyer's premium is recorded within Inventory Sales. The carrying value of Inventory sold during a period is recorded within Cost of Inventory Sales. Revenue Recognition (Finance Revenues) —Finance revenues consist principally of interest income earned on Notes Receivable. Such interest income is recognized when earned, based on the amount of the outstanding loan, the applicable interest rate on the loan, and the length of time the loan is outstanding during the period. A non-accrual loan is a loan for which future Finance revenue is not recorded due to our determination that it is probable that future interest on the loan is not collectible. Any cash receipts subsequently received on non-accrual loans are first applied to reduce the recorded principal balance of the loan, with any proceeds in excess of the principal balance then applied to interest owed by the borrower. The recognition of Finance revenue may resume on a non-accrual loan if sufficient additional collateral is provided by the borrower or if we become aware of other circumstances that indicate that it is probable that the borrower will make future interest payments on the loan. See Note 4 for information related to Notes Receivable. Revenue Recognition (Advisory Revenues) —Advisory revenues consist of fees earned from providing art-related advice to certain clients. These arrangements may be evidenced by a legally binding written agreement between us and the client, which outlines the nature of the services to be provided and the amount of fees to be earned. Our advisory services are also some

Segment Reporting

Segment Reporting	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting Sotheby's offers collectors the opportunity to connect with and transact in the world's most extraordinary art and luxury goods. Auctioneers since 1744, today we present auctions in ten different salesrooms, including New York, London, Hong Kong and Paris, and Sotheby’s BidNow program allows clients to view all auctions live online and place bids on their mobile devices from anywhere in the world. We also offer collectors a variety of innovative art-related services, including the brokerage of private art sales, private jewelry sales through Sotheby's Diamonds, exclusive private selling exhibitions, art-related financing, and art advisory services, as well as retail wine locations in New York and Hong Kong. Our operations are organized under two segments—the Agency segment and the Finance segment, which does business as and is referred to in this report as Sotheby's Financial Services (or "SFS"). Thomas S. Smith, Jr, Sotheby's CEO, is our chief operating decision maker. Mr. Smith regularly evaluates financial information about each of our segments in deciding how to allocate resources and assess performance. The performance of each segment is measured based on segment income before taxes, which excludes the unallocated items highlighted in the reconciliation below. Through our Agency segment, we accept property on consignment, stimulate buyer interest through professional marketing techniques, and match sellers (also known as consignors) to buyers through the auction or private sale process. Prior to offering a work of art for sale, we perform due diligence activities to authenticate and determine the ownership history of the property being sold. To a much lesser extent, the Agency segment also includes the sale of artworks that are owned by Sotheby's, principally as a consequence of the auction process, as well as our investment in RM Sotheby's, an auction house for investment-quality automobiles. The Agency segment is an aggregation of the auction, private sale, and other related activities conducted by our operating segments in the Americas, Europe, and Asia, which have similar economic characteristics and are similar in their services, customers, and the manner in which their services are provided. SFS is an art financing company that operates as a niche lender with the ability to tailor attractive financing packages for clients who wish to obtain immediate access to liquidity from their art assets. SFS leverages the art expertise of the Agency segment, skill in international law and finance, and access to capital to provide art collectors and dealers with financing secured by their works of art, allowing them to unlock the value in their collections. Art Agency, Partners (“AAP”), which was acquired on January 11, 2016 (see Note 3) and through which we offer art advisory services, provides art collectors with strategic guidance on collection identity and development, acquisitions, short and long-term planning, and provides advice to artists and artists' estates. In addition, from time-to-time, AAP brokers private art sales for its advisory clients. Our advisory services are classified within All Other for segment reporting purposes, along with our retail wine business, brand licensing activities, and the results from certain equity method investments (see Note 5). The following table presents our segment information for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars): Year ended December 31, 2017 Agency SFS All Other Reconciling items Total Revenues $ 907,557 $ 60,105 $ 30,895 $ (9,168 ) (a) $ 989,389 Interest income $ 1,184 $ — $ — $ — $ 1,184 Interest expense $ 32,218 $ — $ — $ — $ 32,218 Depreciation and amortization $ 23,015 $ 244 $ 794 $ — $ 24,053 Segment income before taxes $ 101,203 $ 32,295 $ 10,696 $ (2,508 ) (b) $ 141,686 Year ended December 31, 2016 Revenues $ 726,662 $ 61,234 $ 25,999 $ (8,518 ) (a) $ 805,377 Interest income $ 1,294 $ — $ — $ — $ 1,294 Interest expense $ 30,310 $ — $ — $ — $ 30,310 Depreciation and amortization $ 21,081 $ 119 $ 617 $ — $ 21,817 Segment income (loss) before taxes $ 64,571 (c) $ 35,907 $ (482 ) (c) $ (3,262 ) (b) $ 96,734 Year ended December 31, 2015 Revenues $ 892,030 $ 65,248 $ 18,975 $ (14,759 ) (a) $ 961,494 Interest income $ 1,773 $ 3 $ — $ — $ 1,776 Interest expense $ 32,745 $ — $ — $ — $ 32,745 Depreciation and amortization $ 19,233 $ 124 $ 124 $ — $ 19,481 Segment income before taxes $ 139,942 $ 41,303 $ 10,864 $ (22,810 ) (b) $ 169,299 (a) The reconciling items related to Revenues consist principally of amounts charged by SFS to the Agency segment, including interest and facility fees related to certain loans made to Agency segment clients, as well as fees charged for term loan collateral sold at auction or privately through the Agency segment. (b) The reconciling items related to segment income before taxes are detailed in the table below. (c) Agency segment income before taxes for the year ended December 31, 2016 includes $23.9 million of compensation expense related to an earn-out arrangement with the former principals of AAP. All Other income (loss) before taxes for the year ended December 31, 2016 includes $11.1 million of compensation expense related to this earn-out arrangement. See Note 3 . The table below presents a reconciliation of segment income (loss) before taxes to consolidated income before taxes for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars): 2017 2016 2015 Agency $ 101,203 $ 64,571 $ 139,942 SFS 32,295 35,907 41,303 All Other 10,696 (482 ) 10,864 Segment income before taxes 144,194 99,996 192,109 Unallocated amounts and reconciling items: Leadership transition severance costs (a) — — (13,251 ) CEO separation and transition costs (see Note 23) — — (4,232 ) Equity in earnings of investees (b): (2,508 ) (3,262 ) (5,327 ) Income before taxes $ 141,686 $ 96,734 $ 169,299 (a) In 2015, in conjunction with our leadership transition, we incurred severance costs of $13.3 million associated with the termination of certain executive officers, including our former Chief Financial Officer and former Chief Operating Officer. (b) For segment reporting purposes, our share of earnings related to equity investees is included as part of income before taxes. However, such earnings are reported separately below income before taxes in our Consolidated Income Statements. See Note 5 for information related to our equity method investments. The table below presents geographic information about our revenues for the years ended December 31, 2017 , 2016 , and 2015 for all countries which exceeded 5% of total revenues (in thousands of dollars): 2017 2016 2015 United States $ 383,918 $ 367,200 $ 463,129 United Kingdom 229,586 193,721 257,336 Hong Kong and China 223,258 145,885 146,262 Switzerland 95,653 50,003 50,134 France 52,872 42,980 41,803 Other countries 13,270 14,106 17,589 Reconciling item: Intercompany revenue (9,168 ) (8,518 ) (14,759 ) Total $ 989,389 $ 805,377 $ 961,494 The table below presents segment assets, as well as a reconciliation of segment assets to consolidated assets as of December 31, 2017 , 2016 , and 2015 (in thousands of dollars): December 31, 2017 2016 2015 Agency $ 2,395,429 $ 1,759,670 $ 2,499,441 SFS 608,713 687,649 721,781 All Other 40,566 42,246 25,178 Total segment assets 3,044,708 2,489,565 3,246,400 Unallocated amounts and reconciling items: Deferred tax assets and income tax receivable 42,599 14,861 16,913 Consolidated assets $ 3,087,307 $ 2,504,426 $ 3,263,313 Substantially all of our capital expenditures for the years ended December 31, 2017 , 2016 , and 2015 were attributable to the Agency segment.

Acquisition of Art Agency, Part

Acquisition of Art Agency, Partners	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisition of Art Agency, Partners	Acquisition of Art Agency, Partners On January 11, 2016, we acquired Art Agency, Partners, a firm that provides a range of art-related services, in exchange for initial cash consideration of $50 million and future earn-out payments of up to $35 million , as discussed in more detail below. The purpose of this acquisition is to grow auction and private sale revenues by enhancing our relationships with art collectors and by improving our position in the fine art market, particularly in Impressionist, Modern and Contemporary Art. Also, as a result of this acquisition, we have added a new revenue stream by integrating AAP's existing art advisory business, providing a new avenue for growth. The purchase agreement governing the acquisition of AAP includes non-competition and non-solicitation covenants that continue in effect until January 2021. In connection with this acquisition, each of the former principals of AAP also entered into a five -year employment agreement that extends through January 2021. Each employment agreement also includes non-competition and non-solicitation covenants that continue in effect for 12 months following the end of employment. As indicated above, in connection with the acquisition of AAP, we agreed to make future earn-out payments to the former principals of AAP not to exceed $35 million in the aggregate, contingent on the achievement of a level of cumulative financial performance within the Impressionist, Modern and Contemporary Art collecting categories, as well as from AAP's art advisory business. Progress against the cumulative financial target (the "Target") was to be measured at the end of each calendar year during the four -year performance period following the acquisition, after adjusting the Target to reflect the annual growth or contraction of the auction market for Impressionist, Modern and Contemporary Art, when compared to the year ended December 31, 2015. Amounts owed pursuant to the earn-out arrangement are considered to be compensation expense for accounting purposes and are classified within Salaries and Related Costs in our Consolidated Income Statements. For the year ended December 31, 2016 , we recognized $35 million of compensation expense associated with the AAP earn-out arrangement, reflecting the full achievement of the Target as a result of our improved market share in the Contemporary Art collecting category, as well as an improvement in auction commission margins, during the initial annual period. The $35 million owed under the earn-out arrangement is being paid in four annual increments of $8.75 million in the first quarter of each year beginning in 2017 and through 2020. The portion of the accrued liability due in the first quarter of 2018 ( $8.75 million) is recorded within Accrued Salaries and Related Costs on our Consolidated Balance Sheets. The remaining liability ( $17.5 million) is recorded within Other Long-Term Liabilities. See Note 12 . The table below summarizes the allocation of the total purchase price paid for AAP to the assets acquired and liabilities assumed (in thousands of dollars): Purchase price: Initial cash consideration $ 50,000 Working capital adjustment 1,189 Total purchase price $ 51,189 Allocation of purchase price: Net working capital acquired $ 1,572 Fixed assets and other long-term assets 173 Goodwill 34,490 Intangible assets - customer relationships (see Note 7) 10,800 Intangible assets - non-compete agreements (see Note 7) 3,060 Deferred tax assets 1,094 Total purchase price $ 51,189 Upon completion of the purchase price allocation in the second quarter of 2016, $28.3 million of the resulting goodwill was allocated to the Agency segment and $6.2 million was allocated to the acquired art advisory business, which is reported within All Other for segment reporting purposes. The goodwill is tax deductible over a period of 15 years. We incurred $0.8 million of transaction costs in connection with the acquisition of AAP, which were recognized within General and Administrative Expenses in our Consolidated Income Statements in the fourth quarter of 2015 ( $0.6 million ) and the first quarter of 2016 ( $0.2 million ). It is impracticable to compute the amount of revenues and earnings contributed to the Agency segment as a result of the acquisition because the related activities have been integrated into the segment. Disclosure of pro-forma revenues and earnings attributable to the acquisition is also excluded because it is impracticable to determine since AAP was a closely-held private entity and its historical financial records are not available in U.S. GAAP.

Receivables

Receivables	12 Months Ended
	Dec. 31, 2017
Accounts and Notes Receivable, Net [Abstract]
Receivables	Receivables Accounts Receivable, Net —Through our Agency segment, we accept property on consignment and match sellers, also known as consignors, to buyers through the auction or private sale process. Following an auction or private sale, we invoice the buyer for the purchase price of the property (including any commissions, as well as any applicable taxes and royalties), collect payment from the buyer, and remit to the consignor the net sale proceeds after deducting our commissions, expenses and applicable taxes and royalties. The amount invoiced to the buyer is recorded on our Consolidated Balance Sheets within Accounts Receivable, Net. Under our standard auction payment terms, the purchase price is due from the buyer no more than 30 days after the sale date, with the net proceeds due to the consignor 35 days after the sale date. For private sales, payment from the buyer is typically due on the sale date, with the net sale proceeds due to the consignor shortly thereafter. We also sometimes provide extended payment terms to an auction or private sale buyer. For auctions, the extent to which extended payment terms are provided can vary considerably from selling season to selling season. Extended payment terms typically extend the payment due date to a date that is no longer than one year from the sale date. In limited circumstances, the payment due date may be extended to a date that is beyond one year from the sale date. When providing extended payment terms, we attempt to match the timing of cash receipt from the buyer with the timing of our payment to the consignor, but are not always successful in doing so. All extended payment term arrangements are approved by management under our internal corporate governance policy. In the limited circumstances when the buyer's payment due date is extended to a date that is beyond one year from the sale date, if the consignor does not provide matched payment terms (i.e., we pay the consignor before receiving payment from the buyer), the receivable balance is reclassified from Accounts Receivable (net) to Notes Receivable (net) on our Consolidated Balance Sheets. As of December 31, 2017 and 2016 , Notes Receivable (net) within the Agency segment included $2.7 million and $7.5 million , respectively, of such balances that have been reclassified from Accounts Receivable (net). See our discussion of Agency segment notes receivable below. Under the standard terms and conditions of our auction and private sales, we are not obligated to pay the consignor for property that has not been paid for by the buyer. If a buyer defaults on payment, the sale is cancelled, and the property is returned to the consignor. Alternatively, the consignor may reoffer the property at one of our future auctions or negotiate a private sale with us acting as their agent. In certain instances, and subject to management approval under our internal corporate governance policy, we may pay the net sale proceeds to the consignor before payment is collected from the buyer and/or we may allow the buyer to take possession of the property before making payment. In situations when the buyer takes possession of the property before making payment, we are liable to the seller for the net sales proceeds whether or not the buyer makes payment . As of December 31, 2017 and 2016 , Accounts Receivable (net) included $92.1 million and $90.1 million , respectively, related to situations when we paid the consignor all or a portion of the net sales proceeds before payment was collected from the buyer. As of December 31, 2017 and 2016 , Accounts Receivable (net) also included $53.8 million and $76.3 million , respectively, related to situations when we allowed the buyer to take possession of the property before making payment. Notes Receivable (Sotheby's Financial Services) —SFS makes term loans secured by artworks that are not presently intended for sale, allowing us to establish or enhance mutually beneficial relationships with art collectors. Term loans may also generate future auction or private sale consignments through the sale of the collateral at the conclusion of the loan and/or through future purchases of new property by the borrower. In certain situations, term loans are made to refinance receivables generated by the auction and private sale purchases of our clients. Term loans normally have initial maturities of up to two years and typically carry a variable market rate of interest. To a much lesser extent, SFS also makes consignor advances secured by artworks that are contractually committed, in the near term, to be offered for sale through our Agency segment. Consignor advances allow sellers to receive funds upon consignment for an auction or private sale that will occur up to one year in the future and normally have short-term maturities. The lending activities of SFS are funded by borrowings drawn from the SFS Credit Facility, a dedicated revolving credit facility, and with cash balances, including amounts generated by the Agency segment. See Note 9 for information related to the dedicated revolving credit facility for SFS. As of December 31, 2017 and 2016 , the net Notes Receivable balance of SFS was $590.6 million and $675.1 million , respectively. As of December 31, 2017 and 2016 , these loan portfolio balances include $54.4 million and $88.7 million , respectively, of term loans issued by SFS to refinance client auction and private sale purchases. For the years ended December 31, 2017 and 2016 , SFS issued $6.5 million and $13.3 million , respectively, of such loans. These loans are accounted for as non-cash transfers between Accounts Receivable (net) and Notes Receivable (net) and are, therefore, not reflected as the funding of Notes Receivable within Investing Activities in our Consolidated Statements of Cash Flows. Upon repayment, the cash received in settlement of such Notes Receivable is classified within Operating Activities in our Consolidated Statements of Cash Flows. For the years ended December 31, 2017 and 2016 , such repayments totaled $40.8 million and $33.4 million , respectively. The repayment of secured loans can be adversely impacted by a decline in the art market in general or in the value of the collateral, which is concentrated within certain collecting categories. In addition, in situations when there are competing claims on the collateral and/or when a borrower becomes subject to bankruptcy or insolvency laws, our ability to realize on our collateral may be limited or delayed. We aim to mitigate the risk associated with a potential devaluation in our collateral by targeting a 50% loan-to-value ("LTV") ratio (i.e., the principal loan amount divided by the low auction estimate of the collateral). However, loans may also be made with LTV ratios between 51% and 60% , and in rare circumstances, loans may be made at an initial LTV ratio higher than 60% . The revolving credit facility for SFS permits borrowings up to 85% of the portion of any loan that does not exceed a 60% LTV ratio. The LTV ratio of certain loans may increase above our 50% target due to a decrease in the low auction estimate of the collateral. The revaluation of term loan collateral is performed by our specialists on an annual basis or more frequently if there is a material change in the circumstances related to the loan, the value of the collateral, the disposal plans for the collateral, or if an event of default occurs. We believe that the LTV ratio is a critical credit quality indicator for the secured loans made by SFS. The table below provides the aggregate LTV ratio for the SFS loan portfolio as of December 31, 2017 and 2016 (in thousands of dollars): December 31, 2017 2016 Secured loans $ 590,609 $ 675,109 Low auction estimate of collateral $ 1,369,235 $ 1,405,856 Aggregate LTV ratio 43 % 48 % The table below provides the aggregate LTV ratio for secured loans made by SFS with an LTV above 50% as of December 31, 2017 and 2016 (in thousands of dollars): December 31, 2017 2016 Secured loans with an LTV ratio above 50% $ 168,116 $ 270,111 Low auction estimate of collateral related to secured loans with an LTV above 50% $ 269,063 $ 486,973 Aggregate LTV ratio of secured loans with an LTV above 50% 62 % 55 % The table below provides other credit quality information regarding secured loans made by SFS as of December 31, 2017 and 2016 (in thousands of dollars): December 31, 2017 2016 Total secured loans $ 590,609 $ 675,109 Loans past due $ 62,570 $ 90,508 Loans more than 90 days past due $ 56,087 $ 158 Non-accrual loans $ — $ 158 Impaired loans $ — $ — Allowance for credit losses: Allowance for credit losses for impaired loans $ — $ — Allowance for credit losses based on historical data 1,253 1,270 Total allowance for credit losses - secured loans $ 1,253 $ 1,270 We consider a loan to be past due when principal payments are not paid by the contractual maturity date. Typically, a loan becomes past due only for a short period of time during which either the loan is renewed or collateral is sold to satisfy the borrower's obligation. As of December 31, 2017 , $62.6 million of the net Notes Receivable balance was past due, of which $56.1 million was more than 90 days past due. We are continuing to accrue interest on $14.8 million of past due loans and, as of December 31, 2017, the collateral securing such loans has a low auction estimate of approximately $96.8 million , resulting in an LTV ratio of 15% . In consideration of the LTV ratio for these loans, current collateral disposal plans, and anticipated loan renewals, we believe that the principal and interest amounts owed on these loans will be collected. A non-accrual loan is a loan for which future Finance Revenue is not recorded due to our determination that it is probable that future interest on the loan will not collectible. Any cash receipts subsequently received on non-accrual loans are first applied to reduce the recorded principal balance of the loan, with any proceeds in excess of the principal balance then applied to interest owed by the borrower. The recognition of Finance Revenue may resume on a non-accrual loan if sufficient additional collateral is provided by the borrower, if proceeds collected from the sale of loan collateral exceed pre-sale estimates, or if we become aware of other circumstances that indicate that it is probable that the borrower will make future interest payments on the loan. As of January 1, 2018, one of the past due loans included in the table above was placed on non-accrual status. As of December 31, 2017 , our recorded investment in this loan was approximately $49.5 million , consisting of the $47.7 million principal balance and $ 1.8 million in accrued interest. Through February 26, 2018, collateral sale proceeds of $ 10.2 million were collected in respect of this loan and $ 23.8 million of additional proceeds from completed collateral sales are expected to be collected from auction and private sale buyers in the first half of 2018. Following the collection of these collateral sale proceeds, our recorded investment in the loan will be $ 15.5 million, and the loan will have an LTV ratio of approximately 100% (excluding any auction and private sale commissions to be earned by the Agency segment on future collateral sales). The remaining collateral related to this loan is expected to be offered for auction and private sales throughout 2018. A loan is considered to be impaired when we determine that it is probable that a portion of the principal and interest owed by the borrower will not be recovered after taking into account the estimated realizable value of the collateral securing the loan, as well as the ability of the borrower to repay any shortfall between the value of the collateral and the amount of the loan. If a loan is considered to be impaired, Finance Revenue is no longer recognized and bad debt expense is recorded for any principal or accrued interest that is deemed uncollectible. As of December 31, 2017 and 2016 , there were no impaired SFS loans outstanding. As of December 31, 2017 , unfunded commitments to extend additional credit through SFS were approximately $51.8 million . Notes Receivable (Agency Segment) —We are obligated under the terms of certain auction guarantees to advance a portion of the guaranteed amount prior to the auction. Such auction guarantee advances are recorded on our Consolidated Balance Sheets within Notes Receivable (net). As of December 31, 2017 , there were no auction guarantee advances outstanding. As of December 31, 2016 , there were $1 million in auction guarantee advances outstanding. See Note 19 for information related to auction guarantees. As discussed above, in the limited circumstances when the payment due date for an auction or private sale receivable is extended to a date that is beyond one year from the sale date, if the consignor does not provide matched payment terms, the receivable balance is reclassified from Accounts Receivable (net) to Notes Receivable (net) on our Consolidated Balance Sheets. As of December 31, 2017 and 2016, Notes Receivable (net) within the Agency segment included $2.7 million and $7.5 million of such amounts reclassified from Accounts Receivable (net), against which we hold $3.1 million of collateral in both years. These Notes Receivable are accounted for as non-cash transfers between Accounts Receivable (net) and Notes Receivable (net) and are, therefore, not reflected as the funding of Notes Receivable within Investing Activities in our Consolidated Statements of Cash Flows. Upon repayment, the cash received in settlement of such Notes Receivable is classified within Operating Activities in our Consolidated Statements of Cash Flows. For the year ended December 31, 2017 and 2016, such repayments totaled $5 million and $16.3 million , respectively. Under certain circumstances, we provide loans to certain art dealers to finance the purchase of works of art. In these situations, we acquire a partial ownership interest or a security interest in the purchased property in addition to providing the loan. Upon the eventual sale of the property acquired, the loan is repaid. As of December 31, 2016, such loans totaled $3.8 million . In the fourth quarter of 2017, we determined one of these loans to be impaired as a result of the bankruptcy of the art dealer and recorded a credit loss of $1.5 million in the period. We have commenced legal proceedings against one of the individuals who personally guaranteed this loan. As of December 31, 2017 , we had one loan outstanding of this type with a balance of $2.1 million . We are are no longer accruing interest on this loan, but we believe that the recorded balance of the loan is collectible. Notes Receivable (Other) —In the second quarter of 2013, we sold our interest in an equity method investee for $4.3 million . The sale price was funded by an upfront cash payment of $0.8 million and the issuance of a $3.5 million unsecured loan. This loan had a variable market rate of interest, required monthly payments during the loan term, and was initially scheduled to mature in December 2018. As of December 31, 2016 , the carrying value of this loan was $2.1 million . The remaining balance of the loan was repaid in the second quarter of 2017. Allowance for Credit Losses —For the years ended December 31, 2017 and 2016 , activity related to the Allowance for Credit Losses by segment was as follows (in thousands of dollars): SFS Agency Total Balance as of January 1, 2016 $ 1,458 $ — $ 1,458 Change in loan loss provision based on historical data (188 ) — (188 ) Balance as of December 31, 2016 1,270 — 1,270 Change in loan loss provision based on historical data (17 ) — (17 ) Change in loan loss provision for impaired loans — 1,525 1,525 Balance as of December 31, 2017 $ 1,253 $ 1,525 $ 2,778

Equity Method Investments

Equity Method Investments	12 Months Ended
	Dec. 31, 2017
Equity Method Investment, Summarized Financial Information [Abstract]
Equity Method Investments	Equity Method Investments Acquavella Modern Art— On May 23, 1990, we purchased the common stock of the Pierre Matisse Gallery Corporation ("Matisse") for approximately $153 million . The assets of Matisse consisted of a collection of fine art (the "Matisse Inventory"). Upon consummation of the purchase, we entered into an agreement with Acquavella Contemporary Art, Inc. ("ACA") to form AMA, a partnership through which the Matisse Inventory would be sold. We contributed the Matisse Inventory to AMA in exchange for a 50% interest in the partnership. The original term of the AMA partnership agreement was due to expire in 2000 and it was renewed on an annual basis through 2016. On April 27, 2017, the AMA partnership agreement was amended to extend the term of the partnership to May 1, 2022. Upon dissolution of AMA, if we and ACA elect not to liquidate the property and assets of AMA, any assets remaining after the payment of expenses and any other liabilities of AMA will be distributed to us and AMA as tenants-in-common or in some other reasonable manner. The net assets of AMA consist almost entirely of the Matisse Inventory. As of December 31, 2017 and 2016 , the carrying value of the Matisse Inventory was $33.9 million and $39 million , respectively. As of December 31, 2017 and 2016 , the carrying value of our investment in AMA was $4.8 million and $7.9 million , respectively. For the years ended December 31, 2017 , 2016 , and 2015 , our results include $1.7 million , $1.3 million , and $2.8 million , respectively, of equity earnings related to AMA. From time-to-time, we transact with the principal shareholder of ACA in the normal course of our business. RM Sotheby's— On February 18, 2015, we acquired a 25% ownership interest in RM Auctions, an auction house for investment-quality automobiles, for $30.7 million . Following our investment, RM Auctions is now known as RM Sotheby's. In addition to the initial 25% ownership interest, we have governance participation through a comprehensive partnership agreement. The terms of our investment provide us with the opportunity to increase our ownership stake over time. As of December 31, 2017 and 2016 , the carrying value of our investment in RM Sotheby's was $36.4 million and $35.3 million , respectively. For the years ended December 31, 2017 , 2016 , and 2015, our results include $1.2 million , $2 million , and $2.5 million , respectively, of equity earnings related to RM Sotheby's. Other— In the second quarter of 2017, we formed a partnership through which artworks are being purchased and sold. As of December 31, 2017, our investment in this partnership was $5.7 million , representing our 50% ownership interest.

Fixed Assets

Fixed Assets	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Fixed Assets	Fixed Assets As of December 31, 2017 and 2016 , Fixed Assets consisted of the following (in thousands of dollars): December 31, 2017 2016 Land $ 92,591 $ 92,155 Buildings and building improvements 235,222 230,803 Leasehold improvements 84,504 72,969 Computer hardware and software 77,179 74,744 Furniture, fixtures and equipment 81,031 76,829 Construction in progress 9,492 3,621 Other 1,767 5,257 Sub-total 581,786 556,378 Less: Accumulated depreciation and amortization (229,751 ) (209,196 ) Total Fixed Assets, net $ 352,035 $ 347,182 We recently completed a review of our New York real estate holdings and concluded that we will continue to occupy our headquarters at 1334 York Avenue in New York for the foreseeable future. In September 2017, we decided to undertake an enhancement program, beginning in June 2018, to create new state-of-the art galleries, as well as new public and client exhibition spaces. As a result of this enhancement program, certain building improvements and other fixed assets will be removed from service before the end of their originally estimated useful lives, resulting in accelerated depreciation expense of $1.9 million recognized in the fourth quarter of 2017. For the years ended December 31, 2017 , 2016 , and 2015 , Depreciation and Amortization related to Fixed Assets was $22.1 million , $19.9 million , and $19.5 million , respectively.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill —As of January 1, 2016, all goodwill was attributable to the Agency segment. As discussed in Note 3, on January 11, 2016, we acquired AAP, a firm that provides a range of art-related services. Upon completion of the related purchase price allocation, $28.3 million of the resulting goodwill was allocated to the Agency segment and $6.2 million was allocated to the acquired art advisory business, which is reported within All Other for segment reporting purposes. On November 30, 2016, we acquired Orion Analytical, a materials analysis and consulting firm that utilizes state-of-the-art technical and scientific methods in the examination of art, cultural property, wine and other objects. With this acquisition, we have established a scientific research department that complements our existing world-class expertise and provenance research capabilities. For the years ended December 31, 2017 and 2016, changes in the carrying value of Goodwill were as follows (in thousands of dollars): Year ended December 31, 2017 Year ended December 31, 2016 Agency All Other Total Agency All Other Total Beginning balance as of January 1, $ 43,878 $ 6,151 $ 50,029 $ 13,621 $ — $ 13,621 Goodwill acquired: AAP (see Note 3) — — — 28,339 6,151 34,490 Orion Analytical — — — 2,445 — 2,445 Foreign currency exchange rate changes 518 — 518 (527 ) — (527 ) Ending balance as of December 31, $ 44,396 $ 6,151 $ 50,547 $ 43,878 $ 6,151 $ 50,029 Intangible Assets —As of December 31, 2017 and 2016 , intangible assets consisted of the following (in thousands of dollars): Amortization Period December 31, 2017 December 31, 2016 Indefinite lived intangible assets: License (a) N/A $ 324 $ 324 Intangible assets subject to amortization: Customer relationships - AAP (see Note 3) 8 years 10,800 10,800 Non-compete agreements - AAP (see Note 3) 6 years 3,060 3,060 Artworks database (b) 10 years 1,200 1,125 Total intangible assets subject to amortization 15,060 14,985 Accumulated amortization (3,892 ) (1,916 ) Total amortizable intangible assets (net) 11,168 13,069 Total intangible assets (net) $ 11,492 $ 13,393 (a) Relates to a license obtained in conjunction with the purchase of a retail wine business in 2008. (b) Relates to a database containing historic information concerning repeat sales of works of art. This database was acquired with the associated business in exchange for an initial cash payment made in the third quarter of 2016 and a subsequent cash payment made in the third quarter of 2017. For the years ended December 31, 2017 and 2016, amortization expense related to intangible assets was approximately $2 million and $1.9 million , respectively. No such amortization expense was recognized in 2015. The estimated aggregate amortization expense for the remaining useful lives of intangible assets subject to amortization during the five -year period succeeding the December 31, 2017 balance sheet date are as follows (in thousands of dollars): Period Amount 2018 $ 1,980 2019 $ 1,980 2020 $ 1,980 2021 $ 1,980 2022 $ 1,470

Pension Arrangements

Pension Arrangements	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Pension Arrangements	Pension Arrangements Retirement Savings Plan —We sponsor a qualified defined contribution plan for our employees in the U.S. (the "Retirement Savings Plan"). Participants in the Retirement Savings Plan that are below Senior Vice President-level may elect to contribute between 2% and 50% of their eligible compensation, on a pre-tax or after-tax Roth basis. Participants in the Retirement Savings Plan that are Senior Vice President-level and above may elect to contribute between 2% and 25% of their eligible compensation, on a pre-tax or after-tax Roth basis. We may match participant savings with a contribution of up to 3% of eligible employee compensation. We may also contribute an annual discretionary amount to the Retirement Savings Plan, which varies as a percentage of each participant's eligible compensation depending on our profitability. For the year ended December 31, 2017 , we accrued discretionary contributions of $2.1 million , which is equal to 3% of eligible compensation paid during the current year. For the years ended December 31, 2016 and 2015, we accrued discretionary contributions of $1.2 million and $1.3 million , respectively, related to the Retirement Savings Plan, which is equal to 2% of eligible compensation paid during those years. For the years ended December 31, 2017 , 2016 , and 2015 , total pension expense related to matching and discretionary contributions to the Retirement Savings Plan, net of forfeitures, was $3.7 million , $2.5 million , and $2.4 million , respectively. Both participant and Company contributions to the Retirement Savings Plan are subject to limitations under IRS regulations. Deferred Compensation Plan —We sponsor a non-qualified Deferred Compensation Plan (the "DCP"), which is available to certain U.S. officers for whom contributions to the Retirement Savings Plan are limited by IRS regulations. The DCP provides participants with a menu of investment crediting options that track a portfolio of various deemed investment funds. We credit participant accounts on the same basis as matching and discretionary contributions to the Retirement Savings Plan, as discussed above. For the year ended December 31, 2017 , we accrued discretionary contributions of $0.5 million related to the DCP, which is equal to 3% of eligible compensation paid during the current year. For the years ended December 31, 2016 and 2015, we recorded discretionary accruals of $0.3 million related to the DCP, which is equal to 2% of eligible compensation paid during those years. For the years ended December 31, 2017 , 2016 , and 2015 , total pension expense related to our matching and discretionary contributions to the DCP was $0.9 million , $0.6 million , and $0.8 million , respectively. Employee deferrals and our accrued contributions to the DCP are informally funded into a rabbi trust which provides benefit security by sheltering assets in the event of a change-in-control of Sotheby's and certain other situations. DCP liabilities are financed through the trust almost entirely by using company-owned variable life insurance ("COLI"), and, to a much lesser extent, investments in money market mutual funds. As of December 31, 2017 and 2016 , the DCP liability was $25.6 million and $25.9 million , respectively, and the assets held in the rabbi trust consisted of the following (in thousands of dollars): December 31, 2017 2016 Company-owned variable life insurance $ 25,567 $ 25,114 Money market mutual fund investments 673 1,599 Total $ 26,240 $ 26,713 The COLI and money market mutual fund investments are aggregated and recorded on our Consolidated Balance Sheets within Trust Assets Related to Deferred Compensation Liability. The COLI is reflected at its cash surrender value. The money market mutual fund investments are classified as trading securities and reflected at their fair value. Changes in the fair value of the DCP liability, which result from gains and losses in deemed participant investments, are recognized in our Consolidated Income Statements within Salaries and Related Costs in the period in which they occur. Gains in deemed participant investments increase the DCP liability, as well as Salaries and Related Costs. Losses in deemed participant investments decrease the DCP liability, as well as Salaries and Related Costs. For the years ended December 31, 2017 , 2016 , and 2015 , net gains (losses) in deemed participant investments totaled $3.1 million , $1.6 million , and ($0.5) million , respectively. Gains and losses resulting from changes in the cash surrender value of the COLI and the fair value of the money market mutual fund investments, as well as COLI-related expenses, are recognized in our Consolidated Income Statements below Operating Income within Non-Operating Income (Expense) in the period in which they occur. For the years ended December 31, 2017 , 2016 , and 2015 , net gains (losses) related to the COLI and the money market mutual fund investments were $2.6 million , $0.4 million , and ($2.7) million , respectively. In 2015, Non-Operating Expense also includes a $1.6 million death benefit recognized in the fourth quarter of 2015 under the COLI policy. U.K. Defined Contribution Plan —Beginning on April 1, 2004, a defined contribution plan was made available to employees in the U.K. (the "U.K. Defined Contribution Plan"). We may also contribute an annual discretionary amount to the U.K. Defined Contribution Plan, which varies as a percentage of each participant's eligible compensation depending on our profitability. For the year ended December 31, 2017 , we accrued discretionary contributions of $1.1 million related to the U.K. Defined Contribution Plan, which is equal to 3% of eligible compensation paid during the current year. For the years ended December 31, 2016 and 2015, we accrued discretionary contributions of $1.1 million and $0.7 million , respectively, related to the U.K. Defined Contribution Plan, both of which are equal to 2% of eligible compensation paid during those years. For the years ended December 31, 2017 , 2016 , and 2015 , pension expense related to the U.K. Defined Contribution Plan was $4.5 million , $4.3 million , and $3.1 million , respectively. The increase in pension expense in 2016 when compared to 2015 was primarily attributable to additional contributions made on behalf of previously active participants in our U.K. defined benefit pension plan, who transferred into the U.K. Defined Contribution Plan after the defined benefit pension plan was closed to accrual of future service costs on April 30, 2016. See "U.K Defined Benefit Pension Plan" below. U.K. Defined Benefit Pension Plan —We sponsor a defined benefit pension plan in the U.K. (the "U.K. Pension Plan"). Effective April 1, 2004, participation in the U.K. Pension Plan was closed to new employees. On April 30, 2016, after the completion of a statutory consultation process, the U.K. Pension Plan was closed to accrual of future service costs for active participants, who became participants in the U.K. Defined Contribution Plan. Benefit Obligation, Plan Assets, and Funded Status The table below details the changes in the projected benefit obligation, plan assets, and funded status of the U.K. Pension Plan, as well as the net pension asset recognized on our Consolidated Balance Sheets, as of and for the years ended December 31, 2017 and 2016 (in thousands of dollars): December 31, 2017 2016 Reconciliation of benefit obligation Projected benefit obligation at beginning of year $ 327,619 $ 326,243 Service cost — 1,086 Interest cost 8,053 9,817 Contributions by plan participants — 232 Actuarial (gain) loss (781 ) 64,104 Benefits paid (8,508 ) (12,176 ) Settlement payments (11,880 ) — Foreign currency exchange rate changes 31,373 (61,687 ) Projected benefit obligation at end of year 345,876 327,619 Reconciliation of plan assets Fair value of plan assets at beginning of year 406,195 393,102 Actual return on plan assets 28,827 73,806 Employer contributions — 24,748 Contributions by plan participants — 232 Benefits paid (8,508 ) (12,176 ) Settlement payments (11,880 ) — Foreign currency exchange rate changes 40,068 (73,517 ) Fair value of plan assets at end of year 454,702 406,195 Funded Status Net pension asset $ 108,826 $ 78,576 As of December 31, 2017 and 2016 , the net pension asset of $108.8 million and $78.6 million , respectively, was recorded within Other Long-Term Assets on our Consolidated Balance Sheets (see Note 12). In 2017, we made settlement payments of $11.9 million to plan participants who transferred their accrued benefits from the U.K. Pension Plan to alternative arrangements not associated with Sotheby's. For the year ended December 31, 2016 , we contributed $24.7 million to the U.K. Pension Plan, including $24.2 million contributed in December 2016 in respect of the statutory triennial funding valuation that was completed in that year. This contribution satisfied the resulting statutory funding deficit in-full. We did not make any contributions to the U.K. Pension Plan in 2017, and we do not expect to make any regular contributions in 2018. As of December 31, 2017 and 2016 , the accumulated benefit obligation for the U.K. Pension Plan was $345.8 million and $327.6 million , respectively. Components of Net Pension (Benefit) Cost For the years ended December 31, 2017 , 2016 , and 2015 , the components of the net pension (benefit) cost related to the U.K. Pension Plan are as follows (in thousands of dollars): 2017 2016 2015 Service cost $ — $ 1,086 $ 4,497 Interest cost 8,053 9,817 12,923 Prior service cost 60 — — Expected return on plan assets (14,159 ) (17,798 ) (20,174 ) Amortization of actuarial loss 1,139 — 3,967 Amortization of prior service cost (97 ) — 364 Settlement loss 344 — — Net pension (benefit) cost $ (4,660 ) $ (6,895 ) $ 1,577 Net Gain (Loss) Recognized in Other Comprehensive Income (Loss) The net gain (loss) related to the U.K. Pension Plan, which is recognized net of tax in Other Comprehensive Income (Loss), is generally the result of: (i) actual results differing from previous actuarial assumptions (for example, the expected return on plan assets), (ii) changes in actuarial assumptions between balance sheet dates (for example, the discount rate), and/or (iii) curtailment gains. For the years ended December 31, 2017 , 2016 , and 2015 , the net gain (loss) related to the U.K. Pension Plan was $13.3 million , ($6.5) million , and $29.4 million , respectively. Net Loss Included in Accumulated Other Comprehensive Loss Net gains and (losses) related to the U.K. Pension Plan recognized in Other Comprehensive Income (Loss) are recorded net of tax in the Shareholders' Equity section of our Consolidated Balance Sheets within Accumulated Other Comprehensive Loss. As of December 31, 2017 and 2016 , the net loss related to the U.K. Pension Plan recorded in Accumulated Other Comprehensive Loss was ($1) million and ($14.2) million , respectively. If the amount recorded in Accumulated Other Comprehensive Loss exceeds 10% of the greater of (i) the market-related value of plan assets or (ii) the benefit obligation, that excess amount is amortized as a component of future net pension cost or benefit over the average expected future life of plan participants, which is approximately 29.4 years . The market-related value of plan assets adjusts the market value of plan assets by recognizing changes in fair value over a period of five years. It is expected that approximately $0.3 million ( $0.4 million , pre-tax) of the ($1) million after-tax net loss related to the U.K. Pension Plan will be recognized as a reduction of the net pension benefit anticipated for the year ended December 31, 2018. Assumptions As of and for the years ended December 31, 2017 , 2016 , and 2015 , the following assumptions were used in determining the benefit obligation and net pension (benefit) cost related to the U.K. Pension Plan: Benefit Obligation 2017 2016 Weighted average discount rate 2.5% 2.7% Net Pension (Benefit) Cost 2017 2016 2015 Weighted average discount rate N/A N/A 3.5% Weighted average discount rate - service cost N/A 3.8% 3.5% Weighted average discount rate - interest cost 2.4% 3.4% 3.5% Weighted average rate of compensation increase N/A 4.1% 4.1% Weighted average expected long-term rate of return on plan assets 3.8% 5.2% 5.4% The discount rate represents the approximate weighted average rate at which the obligations of the U.K. Pension Plan could be effectively settled and is based on a yield curve for a selection of high-quality corporate bonds with maturity dates approximating the length of time remaining until individual benefit payment dates. Prior to 2016, the same discount rate was used for the service and interest cost components of the net pension (benefit) cost. In 2016, we elected to use separate discount rates for each of these components. The discount rate used for each component in 2016 contemplates a full yield curve in respect to the expected timing of the cash flows related to these components. In 2017, the measurement of the net pension benefit does not include an assumption of a discount rate to measure service cost due to the closure of the U.K. Pension Plan to the accrual of future service costs, as discussed above. Similarly, as of December 31, 2017 and 2016 , the measurement of the benefit obligation does not include an assumption for future annual compensation increases. The expected long-term rate of return is weighted according to the composition of invested assets and is based on expected future appreciation, as well as dividend and interest yields currently available in the equity and bond markets. In particular, the expected rate of return for growth assets represents our estimate of median annualized returns by asset class. The expected rate of return on debt securities is based on interest yields currently available on long-dated U.K. government bonds and highly-rated corporate bonds. No allowance is made in the expected rate of return for potential market out-performance by fund managers. Plan Assets The investment policy for the U.K. Pension Plan is established by its Trustees in consultation with our management. The Trustees' investment objective is to maximize the return on assets while controlling the level of risk so as to ensure that sufficient assets are available to pay participants' benefits as and when they arise. The Trustees have agreed that a portfolio of assets with some growth content is appropriate, but so as to avoid an undue concentration of risk, a diverse spread of assets is held within the portfolio. The diversification is both within and across asset categories. Professional investment managers are provided target allocation percentages for different categories within each asset class; actual allocation percentages are permitted to fall within a reasonable range of these targets. In setting specific asset allocation targets, the Trustees take advice as required from professional investment advisors and require that the majority of the assets be realizable at short notice. As a result of the closure of the U.K. Pension Plan to the accrual of future service costs in April 2016 and our $24.2 million contribution to the plan in December 2016 (both as discussed above), there has been an improvement in the funded status of the plan. Accordingly, a change in asset allocation was implemented in February 2017, which was intended to reduce investment risk and which resulted in an approximate allocation of 40% to growth assets and 60% to debt securities and cash and cash equivalents. In December 2017, another change in asset allocation was implemented, which is intended to further reduce investment risk and resulted in an approximate allocation of 23% to growth assets and 77% to debt securities and cash and cash equivalents. A small holding in real estate is retained and is not subject to this allocation methodology. The investment managers for the U.K. Pension Plan have some discretion in making investment decisions, subject to the investment mandate set forth by the Trustees. It is the Trustees' policy not to invest in the common stock of Sotheby's or any of its subsidiaries. The performance of the investment managers is benchmarked against suitable indices. The table below presents the fair value of U.K. Pension Plan assets, by investment category, as of December 31, 2017 and 2016 (in thousands of dollars): December 31, 2017 % of Total 2016 % of Total Growth assets $ 104,735 23.0 % $ 217,730 53.6 % Debt securities : Corporate 41,804 9.2 % 35,973 8.9 % Index-linked 219,428 48.3 % 134,972 33.2 % Total debt securities 261,232 57.5 % 170,945 42.1 % Real estate mutual funds 3,233 0.6 % 2,667 0.6 % Cash and cash equivalents 85,502 18.8 % 14,853 3.7 % Total fair value of plan assets $ 454,702 $ 406,195 The assets of the U.K. Pension Plan, which are measured at fair value, are classified and disclosed according to one of the following categories: • Level 1—Quoted prices are available in active markets for identical assets or liabilities as of the reporting date. Level 1 inputs generally provide the most reliable evidence of fair value. • Level 2—Pricing inputs are other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date, and fair value may be determined through the use of models or other valuation methodologies. • Level 3—Pricing inputs are unobservable for the asset or liability and include situations where there is little, if any, market activity for the investment. The inputs into the determination of fair value require significant management judgment or estimation. The table below provides fair value measurement information for the U.K. Pension Plan assets as of December 31, 2017 (in thousands of dollars): Fair Value Measurements Using: Total Fair Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Growth assets $ 104,735 $ 104,735 $ — $ — Debt securities: Corporate 41,804 41,804 — — Index-linked 219,428 219,428 — — Total debt securities 261,232 261,232 — — Real estate mutual funds 3,233 — 3,233 — Cash and cash equivalents 85,502 85,502 — — Total fair value of plan assets $ 454,702 $ 451,469 $ 3,233 $ — As of December 31, 2017 , the following U.K. Pension Plan assets are classified as Level 1 fair value measurements: Growth Assets —Includes investments in a publicly-traded mutual fund, the fair value of which is based on exchange quoted prices in active markets. Debt Securities —Includes investments in publicly-traded bond mutual funds, the fair values of which are based on exchange quoted prices in active markets. Cash and Cash Equivalents —Includes investments in cash and money market instruments that are highly liquid and for which book value approximates fair value. As of December 31, 2017 , the following U.K. Pension Plan assets are classified as Level 2 fair value measurements: Real Estate Mutual Funds —Includes investments in real estate mutual funds, the fair value of which are based on directly and indirectly observable real estate prices, including comparable prices. Estimated Future Benefit Payments Estimated future benefit payments related to the U.K. Pension Plan are as follows (in thousands of dollars): Year Benefit Payments 2018 $ 9,323 2019 $ 8,798 2020 $ 9,729 2021 $ 12,013 2022 $ 11,362 2023 to 2027 $ 66,252

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt Instruments [Abstract]
Debt	Debt Revolving Credit Facilities —We are party to a credit agreement with an international syndicate of lenders, which provides for dedicated revolving credit facilities for the Agency segment (the "Agency Credit Facility") and SFS (the "SFS Credit Facility") (the "Credit Agreement"). The maturity date of the Credit Agreement is August 22, 2020. The Agency Credit Facility and the SFS Credit Facility are asset-based revolving credit facilities which may be used primarily for working capital and other general corporate needs, including for the funding of SFS loans. The Credit Agreement allows the proceeds from borrowings under each of the revolving credit facilities to be transferred between the Agency segment and SFS. On October 2, 2017, we reduced the borrowing capacity of the SFS Credit Facility by $235 million . This reduction, which was entirely at our option and as part of our ongoing capital allocation process, was execute d in order to reduce facility fees for unused borrowing capacity. Taking into account this reduction, the maximum aggregate borrowing capacity of the Credit Agreement, which is subject to a borrowing base, is $1.1 billion , with $300 million committed to the Agency segment and $800 million committed to SFS. The borrowing capacity of the Agency Credit Facility includes a $50 million incremental revolving credit facility with higher advance rates against certain assets and higher commitment and borrowing costs (the "Incremental Facility"). On July 25, 2017, the maturity date of the Incremental Facility was extended by one year to August 22, 2018, in accordance with the terms of the Credit Agreement. This maturity date may be extended for an additional 365 days on an annual basis with the consent of the lenders who agree to extend their commitments under the Incremental Facility. The Credit Agreement has a sub-limit of $320 million for foreign currency borrowings, with up to $50 million available for foreign currency borrowings under the Agency Credit Facility and up to $270 million available for foreign currency borrowings under the SFS Credit Facility. The Credit Agreement also includes an accordion feature, which allows us to seek an increase to the borrowing capacity of the Credit Agreement until February 23, 2020 by an amount not to exceed $150 million in the aggregate. Though new commitments would need to be obtained, the uncommitted accordion feature permits us to seek an increase to the aggregate commitments of the Credit Agreement under an expedited arrangement process. The borrowing base under the Agency Credit Facility is determined by a calculation that is primarily based upon a percentage of the carrying values of certain auction guarantee advances (see Note 4 ), a percentage of the carrying value of certain inventory (see Note 1), a percentage of the carrying value of certain extended payment term receivables arising from auction or private sale transactions (see Note 4 ), and the fair value of certain of our trademarks. The borrowing base under the Incremental Facility is determined by a calculation that is based on a percentage of the carrying values of certain inventory and the fair value of certain of our trademarks. The borrowing base under the SFS Credit Facility is determined by a calculation that is primarily based on a percentage of the carrying value of certain SFS loans (see Note 4) and the fair value of certain our trademarks. The obligations under the Credit Agreement are cross-guaranteed and cross-collateralized. Domestic borrowers are jointly and severally liable for all obligations under the Credit Agreement and, subject to certain limitations, borrowers in the U.K. and Sotheby's Hong Kong Limited are jointly and severally liable for all obligations of the foreign borrowers under the Credit Agreement. In addition, the obligations of the borrowers under the Credit Agreement are guaranteed by certain of their subsidiaries. Our obligations under the Credit Agreement are secured by liens on all or substantially all of the personal property of the entities that are borrowers and guarantors under the Credit Agreement. The Credit Agreement contains certain customary affirmative and negative covenants including, but not limited to, limitations on capital expenditures , limitations on indebtedness and limitations on the use of proceeds from borrowings under the Credit Agreements. The Credit Agreements also contain a $600 million limitation on net outstanding auction guarantees (i.e., auction guarantees less the impact of related risk and reward sharing arrangements). The Credit Agreement does not limit dividend payments and common stock repurchases provided that, both before and after giving effect thereto: (i) there are no events of default, (ii) the aggregate available borrowing capacity equals or exceeds $100 million , and (iii) the Liquidity Amount, as defined in the Credit Agreement, equals or exceeds $200 million . The Credit Agreement also contains certain financial covenants, which are only applicable during certain defined compliance periods. These financial covenants were not applicable for the twelve month period ended December 31, 2017 . Since August 2009, we have incurred aggregate fees of approximately $21.8 million in conjunction with the establishment of and subsequent amendments to the Credit Agreement. These fees are being amortized on a straight-line basis through the August 22, 2020 maturity date of the Credit Agreement. As of December 31, 2017 , $5.4 million of such unamortized fees are included within Other Long-Term Assets on our Consolidated Balance Sheets. The following tables summarize information related to the Credit Agreement as of and for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars): As of and for the year ended December 31, 2017 Agency Credit Facility SFS Credit Facility Total Maximum borrowing capacity $ 300,000 $ 800,000 $ 1,100,000 Borrowing base $ 148,299 $ 457,628 $ 605,927 Borrowings outstanding $ — $ 196,500 $ 196,500 Available borrowing capacity (a) $ 148,299 $ 261,128 $ 409,427 Average borrowings outstanding $ — $ 479,367 $ 479,367 Borrowing Costs: Interest $ — (b) $ 15,964 (c) $ 15,964 Fees 2,740 (b) 3,348 (c) 6,088 Total $ 2,740 $ 19,312 $ 22,052 As of and for the year ended December 31, 2016 Agency Credit Facility SFS Credit Facility Total Maximum borrowing capacity $ 300,000 $ 1,035,000 $ 1,335,000 Borrowing base $ 165,443 $ 569,021 $ 734,464 Borrowings outstanding $ — $ 565,000 $ 565,000 Available borrowing capacity (a) $ 165,443 $ 4,021 $ 169,464 Average borrowings outstanding $ — $ 534,433 $ 534,433 Borrowing Costs: Interest $ — (b) $ 14,819 (c) $ 14,819 Fees 2,712 (b) 2,919 (c) 5,631 Total $ 2,712 $ 17,738 $ 20,450 As of and for the year ended December 31, 2015 Agency Credit Facility SFS Credit Facility Total Maximum borrowing capacity $ 300,000 $ 1,035,000 $ 1,335,000 Borrowing base $ 225,642 $ 547,586 $ 773,228 Borrowings outstanding $ — $ 541,500 $ 541,500 Available borrowing capacity (a) $ 225,642 $ 6,086 $ 231,728 Average borrowings outstanding $ — $ 541,004 $ 541,004 Borrowing Costs: Interest $ — (b) $ 14,060 (c) $ 14,060 Fees 2,752 (b) 1,720 (c) 4,472 Total $ 2,752 $ 15,780 $ 18,532 Legend: (a) The available borrowing capacity is calculated as the borrowing base less borrowings outstanding. (b) Borrowing costs related to the Agency Credit Facility, which include interest and fees, are reflected in our Consolidated Income Statements as Interest Expense. (c) Borrowing costs related to the SFS Credit Facility are reflected in our Consolidated Income Statements within Cost of Finance Revenues. For the years ended December 31, 2017 , 2016 , and 2015 , the weighted average cost of borrowings related to the SFS Credit Facility was approximately 4.0% , 3.3% , and 2.9% , respectively. For the year ended December 31, 2017, the Cost of Finance Revenues includes a charge of $0.7 million associated with the reduction in the borrowing capacity of the SFS Credit Facility discussed above. Long-Term Debt —As of December 31, 2017 and 2016 , Long-Term Debt consisted of the following (in thousands of dollars): December 31, 2017 2016 York Property Mortgage, net of unamortized debt issuance costs of $4,545 and $5,555 $ 270,556 $ 309,212 2022 Senior Notes, net of unamortized debt issuance costs of $2,998 and $3,642 297,002 296,358 2025 Senior Notes, net of unamortized debt issuance costs of $5,623 and $0 394,377 — Less current portion: York Property Mortgage, net of unamortized debt issuance costs of $1,010 and $1,010 (11,930 ) (6,629 ) 2022 Senior Notes, net of unamortized debt issuance costs of $2,998 and $0 (297,002 ) — Total Long-Term Debt, net $ 653,003 $ 598,941 See the captioned sections below for information related to the York Property Mortgage and our senior unsecured debt, including the 2022 Senior Notes and the 2025 Senior Notes. York Property Mortgage —The York Property, located at 1334 York Avenue, New York, New York, is home to our sole North American auction salesroom and principal North American exhibition space. The York Property is also home to the U.S. operations of SFS, as well as our corporate offices. Upon our acquisition of the York Property in February 2009, we assumed a $235 million mortgage that carried an initial annual rate of interest of approximately 5.6% (the "Original York Property Mortgage"). The Original York Property Mortgage was due to mature on July 1, 2035, but had an optional pre-payment date of July 1, 2015, after which the annual rate of interest was scheduled to increase to 10.6% . On July 1, 2015, we entered into a seven -year, $325 million mortgage loan (the "York Property Mortgage") to refinance the Original York Property Mortgage. After the repayment of the Original York Property Mortgage and the funding of all closing costs, reserves, and expenses, we received net cash proceeds of approximately $98 million . The York Property Mortgage bears interest based on the one -month LIBOR rate (the "LIBOR rate") plus a spread of 2.25% and is being amortized based on a 25 -year mortgage-style amortization schedule over its seven -year term. On June 21, 2017, the York Property Mortgage was amended to reduce the minimum net worth that Sotheby's is required to maintain from $425 million to $325 million in order to provide continued flexibility regarding potential future common stock repurchases. As of December 31, 2017 , Sotheby's net worth was $616.9 million . In conjunction with this amendment, on July 3, 2017, we made a prepayment of $32 million to reduce the outstanding principal balance of the York Property Mortgage, and agreed to make annual prepayments funded exclusively with any cash accumulated in a restricted cash management account (see below) beginning in July 2018 and continuing through July 2021 that are not to exceed $25 million in the aggregate during that period. The $32 million principal payment made on July 3, 2017 was funded with $25 million from existing cash balances and $7 million from the restricted cash management account. See below for information related to the cash management account associated with the York Property Mortgage. In connection with the York Property Mortgage, we entered into interest rate protection agreements secured by the York Property, consisting of a two -year interest rate swap effective as of July 1, 2015 and a five -year interest rate collar effective as of July 1, 2017. See Note 10 for additional information related to these interest rate protection agreements. The York Property, the York Property Mortgage, and the related interest rate protection agreements are held by 1334 York, LLC (the "LLC"), a separate legal entity of Sotheby's that maintains its own books and records and whose results are ultimately consolidated into our Consolidated Financial Statements. The LLC is the sole owner and lessor of the York Property. The LLC presently leases the York Property to Sotheby's, Inc., which is also controlled by Sotheby's. The assets of the LLC are not available to satisfy the obligations of our other affiliates or any other entity. The loan agreement governing the York Property Mortgage contains the following financial covenants, which are subject to additional terms and conditions as provided in the underlying loan agreement: • As of July 1, 2020, the LTV ratio (i.e., the principal balance of the York Property Mortgage divided by the appraised value of the York Property) may not exceed 65% (the "Maximum LTV") based on the then-outstanding principal balance of the York Property Mortgage. If the LTV ratio exceeds the Maximum LTV, the LLC may, at its option, post cash or a letter of credit or pay down the York Property Mortgage without any prepayment penalty or premium, in an amount that will cause the LTV ratio not to exceed the Maximum LTV. • At all times during the term of the York Property Mortgage, the Debt Yield will not be less than 8.5% (the "Minimum Debt Yield"). The Debt Yield is calculated by dividing the annual net operating income of the LLC, which primarily consists of lease income from Sotheby's, Inc. (calculated on a cash basis), by the outstanding principal balance of the York Property Mortgage. If the Debt Yield falls below the Minimum Debt Yield, the LLC has the option to post cash or a letter of credit or prepay the York Property Mortgage without any prepayment penalty or premium, in an amount that will cause the Debt Yield to exceed the Minimum Debt Yield. • If Sotheby's corporate credit rating from Standard & Poor's Rating Services ("S&P") is downgraded to "BB-", the lender may require that the LLC establish cash management accounts (the "Cash Management Accounts") under the lender's control for potential monthly debt service, insurance, and tax payments. If the rating is downgraded to "B+" or "B", the lender may require the LLC to deposit a certain amount of debt service into the Cash Management Accounts (approximately 6 and 12 months of debt service, respectively). If the rating is downgraded to lower than "B", the LLC must make principal payments on the mortgage such that the LTV ratio does not exceed 65% . On February 9, 2016, Sotheby's corporate credit rating from S&P was downgraded to "BB-" from "BB". As a result, a Cash Management Account was established under the control of the lender for monthly debt service, insurance, and tax payments. The lender will retain any excess cash after debt service, insurance, and taxes as security. On July 3, 2017, $7 million from the Cash Management Account was used to fund a portion of the $32 million principal prepayment of the York Property Mortgage discussed above. As of December 31, 2017 and 2016, the Cash Management Account had a balance of $3.1 million and $4.6 million , respectively, which is reflected within Restricted Cash on our Consolidated Balance Sheets. • At all times during the term of the York Property Mortgage, we are required to maintain a net worth of at least $325 million , subject to a cure period. As of December 31, 2017 , the fair value of the York Property Mortgage approximates its book value due to the variable interest rate associated with the mortgage. This fair value measurement is considered to be a Level 2 fair value measurement in the fair value hierarchy as per Accounting Standards Codification 820, Fair Value Measurements ("ASC 820"). Senior Unsecured Debt —On September 27, 2012, we issued $300 million aggregate principal amount of 5.25% Senior Notes, due October 1, 2022 (the "2022 Senior Notes"). The net proceeds from the issuance of the 2022 Senior Notes were approximately $294.6 million , after deducting fees paid to the initial purchasers, and were principally used to retire $80 million of unsecured debt that was due in June 2015 and $182 million of convertible debt that was due in June 2013. As of December 31, 2017 , the $300 million principal amount of 2022 Senior Notes had a fair value of approximately $307.5 million based on a broker quoted price derived via a pricing model using observable and unobservable inputs. As such, this fair value measurement is considered to be a Level 3 fair value measurement in the fair value hierarchy as per ASC 820. On December 12, 2017, we issued $400 million aggregate principal amount of 4.875% Senior Notes due on December 15, 2025 (the “2025 Senior Notes”). The net proceeds from the sale of the 2025 Senior Notes were approximately $395.5 million , after deducting fees paid to the initial purchasers, of which $312.3 million was irrevocably deposited with a trustee for the benefit of the holders of the 2022 Senior Notes, which were redeemed using these funds on January 11, 2018, as discussed below. The $312.3 million deposited with the trustee is classified within Restricted Cash on our Consolidated Balance Sheets as of December 31, 2017. The remaining net proceeds from the issuance of the 2025 Senior Notes are being used for general corporate purposes, including current reductions to revolving credit facility borrowings. Interest on the 2025 Senior Notes is payable in cash semi-annually in arrears on June 15 and December 15 of each year, beginning June 15, 2018. The 2025 Senior Notes were offered only to qualified institutional buyers in accordance with Rule 144A and to non-U.S. Persons under Regulation S under the Securities Act of 1933, as amended (the "Securities Act"). Holders of the 2025 Senior Notes do not have registration rights, and the 2025 Senior Notes have not been and will not be registered under the Securities Act. The 2025 Senior Notes are guaranteed, jointly and severally, on a senior unsecured basis by certain of our existing and future domestic subsidiaries to the extent and on the same basis that such subsidiaries guarantee borrowings under the Credit Agreement. The 2025 Senior Notes will be redeemable, in whole or in part, on or after December 15, 2020, at specified redemption prices set forth in the underlying indenture, plus accrued and unpaid interest to, but excluding, the redemption date. Prior to December 15, 2020, the 2025 Senior Notes are redeemable, in whole or in part, at a redemption price equal to 100% of the principal amount of the 2025 Senior Notes to be redeemed, plus accrued and unpaid interest to, but excluding, the redemption date, plus a make-whole premium (as defined in the underlying indenture). In addition, at any time prior to December 15, 2020, we may redeem up to 40% of the aggregate principal amount of the 2025 Senior Notes with the net cash proceeds of certain equity offerings at the redemption price of 104.875% plus accrued and unpaid interest. If Sotheby's experiences a Change of Control (as defined in the underlying indenture), we must offer to repurchase all of the 2025 Senior Notes then outstanding at 101% of the aggregate principal amount of the 2025 Senior Notes repurchased, plus accrued and unpaid interest. The underlying indenture for the 2025 Senior Notes also contains covenants that limit, among other things, our ability to grant liens on our assets; enter into sale and leaseback transactions; and merge, consolidate or transfer or dispose of substantially all of our assets. The above covenants are subject to a number of exceptions and qualifications set forth in the underlying indenture. As of December 31, 2017 , the $400 million principal amount of the 2025 Senior Notes had a fair value of approximately $392.5 million based on a broker quoted price derived via a pricing model using observable and unobservable inputs. As such, this fair value measurement is considered to be a Level 3 fair value measurement in the fair value hierarchy as per ASC 820. On January 11, 2018, we redeemed the 2022 Senior Notes for a redemption price of $312.3 million , including the $300 million principal amount plus $4.4 million of accrued interest and a call premium of $7.9 million . As a result of the redemption of the 2022 Senior Notes, we will write-off $3 million of related unamortized debt issuance costs, which, when combined with the $7.9 million call premium, will result in a total loss on the extinguishment of $10.9 million , which will be recognized in the first quarter of 2018. Future Payments Due Under Outstanding Debt —The aggregate future principal, interest, and debt settlement payments, including the $7.9 million call premium owed on the 2022 Senior Notes, due during the five year period after December 31, 2017 are as follows (in thousands of dollars): Year Amount 2018 $ 356,264 2019 $ 42,530 2020 $ 238,963 2021 $ 42,931 2022 $ 247,131 The table above assumes that the annual interest rate for the York Property Mortgage will be at the interest rate collar's floor rate of 4.167% for the remainder of the mortgage term and projects principal payments in reference to available forecasts of LIBOR rates for the future periods through maturity. Interest Paid —The table below summarizes interest paid by segment for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars): 2017 2016 2015 Agency $ 33,745 $ 27,793 $ 35,948 SFS 18,062 16,709 17,513 Total $ 51,807 $ 44,502 $ 53,461 Agency segment interest paid primarily relates to the York Property Mortgage, our long-term debt securities, and revolving credit facility fees. SFS interest paid includes interest payments related to the SFS Credit Facility borrowings, including facility fees. In 2017, 2016, and 2015, interest paid includes debt issuance costs of $5.7 million , $0.3 million , and $9.6 million , respectively, which are amortized to Interest Expense in our Consolidated Income Statements.

Derivative Financial Instrument

Derivative Financial Instruments	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Financial Instruments	Derivative Financial Instruments Derivative Financial Instruments Designated as Hedging Instruments —The following tables present fair value information related to the derivative financial instruments designated as hedging instruments as of December 31, 2017 and 2016 (in thousands of dollars): Assets Liabilities December 31, 2017 Balance Sheet Classification Fair Value Balance Sheet Classification Fair Value Cash Flow Hedges: Interest rate swap Other Current Assets $ 339 N/A $ — Interest rate collar N/A — Other Current Liabilities 666 Interest rate collar N/A — Other Long-Term Liabilities 1,501 Total cash flow hedges 339 — 2,167 Net Investment Hedges: Foreign exchange contracts N/A — Other Current Liabilities 3,756 Total $ 339 $ 5,923 Assets Liabilities December 31, 2016 Balance Sheet Classification Fair Value Balance Sheet Classification Fair Value Cash Flow Hedges: Interest rate swaps Other Current Assets $ 82 Other Current Liabilities $ 163 Interest rate collar N/A — Other Long-Term Liabilities 5,952 Total cash flow hedges 82 6,115 Net Investment Hedges: Foreign exchange contracts Other Current Assets 30,258 N/A — Total $ 30,340 $ 6,115 In 2017 , we settled derivative financial instruments designated as net investment hedges with an aggregate notional value of $213.8 million and realized a net gain of $29.1 million . Realized gains and losses related to the settlement of derivative financial instruments designated as net investment hedges are reflected on our Consolidated Balance Sheets within Accumulated Other Comprehensive Loss. The following tables summarize the effect of the derivative financial instruments designated as hedging instruments on our Consolidated Income Statements and Consolidated Statements of Comprehensive Income for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars): Gain (Loss) Recognized in Other Comprehensive Income (Loss) - Effective Portion Classification of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Net Income Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Effective Portion Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Ineffective Portion Year Ended December 31, 2017 2016 2015 2017 2016 2015 2017 2016 2015 Cash Flow Hedges: Interest rate swaps $ 201 $ (704 ) $ (802 ) Interest Expense $ 16 $ 813 $ 688 $ — $ — $ — Interest rate collar 1,219 533 (4,192 ) Interest Expense 577 — — — — — Interest rate collar — — — Non-operating income (expense) — — — 622 — — Total cash flow hedges 1,420 (171 ) (4,994 ) 593 813 688 622 — — Net Investment Hedges: Foreign exchange contracts (3,059 ) 16,618 — N/A — — — — — — Total $ (1,639 ) $ 16,447 $ (4,994 ) $ 593 $ 813 $ 688 $ 622 $ — $ — See the captioned sections below for information related to derivative financial instruments designated as cash flow hedges or as net investment hedges. Derivative Financial Instruments Designated as Cash Flow Hedges —In connection with the York Property Mortgage (see Note 9), we entered into interest rate protection agreements secured by the York Property, consisting of a two -year interest rate swap (the "Mortgage Swap"), effective as of July 1, 2015, and a five -year interest rate collar (the "Mortgage Collar"), effective as of July 1, 2017. The Mortgage Swap fixed the LIBOR rate on the York Property Mortgage at an annual rate equal to 0.877% through its July 1, 2017 expiration date. The Mortgage Collar effectively fixes the LIBOR rate on the York Property Mortgage at an annual rate of no less than 1.917% , but no more than 3.75% , for the remainder of the mortgage's seven -year term. After taking into account the interest rate protection agreements, the annual interest rate for the first two years of the York Property Mortgage was approximately 3.127% and then will be between a floor of 4.167% and a cap of 6% for its remaining seven -year term. Since the effective date of the Mortgage Collar, the effective interest rate for the York Property Mortgage was the Mortgage Collar's floor rate of 4.167% . In conjunction and concurrent with the June 2017 amendment to the York Property Mortgage, the notional value of the Mortgage Collar was reduced by $57 million to reflect: (i) the $32 million principal prepayment made on the York Property Mortgage on July 3, 2017 and (ii) potential annual prepayments of $6.25 million each, beginning in July 2018 and continuing through July 2021. The reduction in the notional value of the Mortgage Collar relates to previously forecasted interest payments that are no longer probable of occurring as a result of the June 2017 amendment to the York Property Mortgage. The reduction in the notional value of the Mortgage Collar resulted in a $0.6 million (net of tax) reclassification from Accumulated Other Comprehensive Loss into Net Income in the second quarter of 2017. As of December 31, 2017, the notional value of the Mortgage Collar was $275.1 million , which is equal to the principal balance of the York Property Mortgage on that date. For the remainder of its term, the Mortgage Collar will have a notional value that is no greater than the applicable forecasted principal balance of the York Property Mortgage. The York Property, the York Property Mortgage, and the related interest rate protection agreement(s) are held by 1334 York, LLC, a separate legal entity of Sotheby's that maintains its own books and records and whose results are ultimately consolidated into our financial statements. On November 21, 2016, we entered into a two -year interest rate swap agreement (the “SFS Swap”) to eliminate the variability in expected cash outflows associated with the one-month LIBOR indexed interest payments owed on $63 million of SFS Credit Facility borrowings. As of December 31, 2017 , the notional value of the SFS Swap was $63 million . See Note 9 for additional information related to the SFS Credit Facility. At their inception, the Mortgage Swap, the Mortgage Collar, and the SFS Swap (collectively, the "Cash Flow Hedges") were each individually designated as cash flow hedges of the risk associated with the variability in expected cash outflows related to the one-month LIBOR-indexed interest payments owed on their respective debt instruments. Accordingly, to the extent that each of the Cash Flow Hedges is effective, any unrealized gains and losses related to changes in their fair value are recorded to Accumulated Other Comprehensive Loss on our Consolidated Balance Sheets and then reclassified to Interest Expense in our Consolidated Income Statements in the same period that interest expense related to the underlying debt instruments is recorded. Any hedge ineffectiveness is immediately recognized in Net Income. In addition, if any of the forecasted transactions associated with the Cash Flow Hedges are no longer probable of occurring, any related amounts previously recorded in Accumulated Other Comprehensive Loss on our Consolidated Balance Sheets would be immediately reclassified into Net Income. As discussed above, certain previously forecasted interest payments associated with the Mortgage Collar became no longer probable of occurring in the second quarter of 2017 and, as a result, $0.6 million (net of tax) of the amount previously recorded in Accumulated Other Comprehensive Loss was immediately reclassified into Net Income in the second quarter of 2017. Management performs a quarterly assessment to determine whether each of the outstanding Cash Flow Hedges continues to be highly effective in hedging the risk associated with the variability in expected cash outflows related to the one-month LIBOR-indexed interest payments on their respective debt instruments. As of December 31, 2017, each of the outstanding Cash Flow Hedges, including the Mortgage Collar, as amended, is expected to continue to be highly effective in hedging the risk associated with the variability in expected cash outflows related to the one-month LIBOR-indexed interest payments on their respective debt instruments. The assets and liabilities associated with the Cash Flow Hedges have been designated as Level 2 fair value measurements within the fair value hierarchy provided by ASC 820. Level 2 fair value measurements have pricing inputs other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date. Level 2 fair value measurements may be determined through the use of models or other valuation methodologies. The fair value of the Mortgage Swap was based on a discounted cash flow methodology using the contractual terms of the instrument and observable LIBOR-curve rates that are consistent with the timing of the interest payments related to the York Property Mortgage. The fair value of the Mortgage Collar is based on an option pricing model using observable LIBOR-curve rates for each forecasted monthly settlement, with the projected cash flows discounted using the contractual terms of the instrument. The fair value of the SFS Swap is based on a discounted cash flow methodology using the contractual terms of the instrument and observable LIBOR-curve rates that are consistent with the timing of the interest payments related to the SFS Credit Facility. Derivative Financial Instruments Designated as Net Investment Hedges —We are exposed to variability in the U.S. Dollar equivalent of the net investments in our foreign subsidiaries and, by extension, the U.S. Dollar equivalent of any foreign earnings repatriated to the U.S. due to potential changes in foreign currency exchange rates. As a result, we regularly enter into foreign currency forward exchange contracts to hedge the net investments in our foreign subsidiaries from which we expect to repatriate earnings to the U.S. As of December 31, 2017 , the aggregate notional value of our outstanding net investment hedge contracts that remained outstanding was $49.7 million . We use the forward rate method to assess the effectiveness of our net investment hedges. Under the forward rate method, if both the notional value of the derivative designated as a hedge of a net investment in a foreign subsidiary equals the portion of the net investment designated as being hedged and the derivative relates solely to the foreign exchange rate between the functional currency of the hedged net investment and the investor’s functional currency, then all changes in fair value of the derivative are reported in the cumulative translation adjustment accounts within Accumulated Other Comprehensive Loss on our Consolidated Balance Sheets. The foreign currency forward exchange contracts designated as net investment hedges are considered Level 2 fair value measurements within the fair value hierarchy provided by ASC 820. Level 2 fair value measurements have pricing inputs other than quoted prices in active markets, which are either directly or indirectly observable as of the reporting date, and fair value may be determined through the use of models or other valuation methodologies. The fair value of these foreign currency forward exchange contracts is based on the estimated amount to settle the contracts using applicable market exchange rates as of the balance sheet date. Derivative Financial Instruments Not Designated as Hedging Instruments —We also utilize forward contracts to hedge cash flow exposures related to foreign currency exchange rate movements arising from short-term foreign currency denominated intercompany balances and, to a much lesser extent, foreign currency denominated client payable balances, as well as foreign currency denominated auction guarantee obligations. Such forward exchange contracts are typically short-term with settlement dates less than six months from their inception. These instruments are not designated as hedging instruments for accounting purposes. Accordingly, changes in the fair value of these instruments are recognized in our Consolidated Income Statements in Non-Operating Income (Expense). As of December 31, 2017 , the notional value of outstanding forward exchange contracts not designated as hedging instruments was $134.4 million . Notional values do not quantify risk or represent our assets or liabilities, but are used to calculate cash settlements under outstanding forward exchange contracts. We are exposed to credit-related risks in the event of nonperformance by the counterparties to our outstanding forward exchange contracts that are not designated as hedging instruments. We do not expect any of these counterparties to fail to meet their obligations, given their investment grade short-term credit ratings. As of December 31, 2017 and 2016, the aggregate fair value of these contracts represented liabilities of $0.8 million and $3.6 million , respectively, which were recorded on our Consolidated Balance Sheets within Accounts Payable and Accrued Liabilities.

Sale of Pink Diamond

Sale of Pink Diamond	12 Months Ended
	Dec. 31, 2017
Other Liabilities Disclosure [Abstract]
Sale of Pink Diamond	Sale of Pink Diamond In the second quarter of 2016, we sold an undivided legal and beneficial 50% ownership interest in a Fancy Vivid Pink Diamond (the "Pink Diamond") held in Inventory for $34.2 million in cash, which was recorded on our Consolidated Balance Sheets as deferred revenue within Other Current Liabilities. In April 2017, at our Magnificent Jewels and Jadeite Sale in Hong Kong (the "Auction"), the Pink Diamond was sold for a total purchase price of approximately $71.2 million (the "Purchase Price"). Although the Auction occurred in the second quarter of 2017, the sale was recognized in our financial statements in the third quarter of 2017 upon collection of the Purchase Price from the winning bidder in September 2017. Upon the collection of the Purchase Price, the $68.4 million carrying value of the Pink Diamond was removed from Inventory, and the related $34.2 million cash payment received in the second quarter of 2016 was removed from Other Current Liabilities. The sale of the Pink Diamond resulted in a gain of approximately $0.4 million in 2017, after taking into account the associated Cost of Inventory Sales of $70.8 million , which includes amounts paid to our partner in the Pink Diamond and other costs related to the sale.

Supplemental Consolidated Balan

Supplemental Consolidated Balance Sheet Information	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Supplemental Consolidated Balance Sheet Information	Supplemental Consolidated Balance Sheet Information As of December 31, 2017 and 2016 , Prepaid Expenses and Other Current Assets consisted of the following (in thousands of dollars): December 31, 2017 2016 Prepaid expenses $ 25,418 $ 20,436 Derivative financial instruments (see Note 10) 339 30,340 Insurance recoveries — 19,884 Other 6,253 5,947 Total Prepaid and Other Current Assets $ 32,010 $ 76,607 The reduction in insurance recoveries reflected in the table above is due to claim proceeds received in 2017, as well as the reclassification of certain insurance recoveries to Other Long-Term Assets based on our reassessment of the timing of the anticipated resolution of the matters involved. In 2017 , we settled derivative financial instruments designated as net investment hedges with an aggregate notional value of $213.8 million and realized a net gain of $29.1 million . See Note 10 for additional information related to derivative financial instruments. As of December 31, 2017 and 2016 , Other Long-Term Assets consisted of the following (in thousands of dollars): December 31, 2017 2016 Defined benefit pension plan asset (see Note 8) $ 108,826 $ 78,576 Equity method investments (see Note 5) 46,905 43,143 Trust assets related to deferred compensation liability (see Note 8) 26,240 26,713 Restricted cash (a) 17,916 1,064 Insurance recoveries 12,242 — Other 15,479 15,928 Total Other Long-Term Assets $ 227,608 $ 165,424 (a) As of December 31, 2017 , restricted cash reflected within Other Long-Term Assets principally relates to $15.3 million of funds held in escrow pending the payment of sale proceeds to a consignor. As of December 31, 2016 , restricted cash reflected within Other Long-Term Assets primarily consisted of segregated cash related to long-term lease arrangements. As of December 31, 2017 and 2016 , Other Long-Term Liabilities consisted of the following (in thousands of dollars): December 31, 2017 2016 Deferred compensation liability (see Note 8) $ 25,614 $ 25,914 Acquisition earn-out consideration (see Note 3) 17,500 26,250 Interest rate collar liability (see Note 10) 1,501 5,952 Other 6,809 6,964 Total Other Long-Term Liabilities $ 51,424 $ 65,080

Supplemental Consolidated Cash

Supplemental Consolidated Cash Flow Information	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Information [Abstract]
Supplemental Consolidated Cash Flow Information	Supplemental Consolidated Cash Flow Information For the years ended December 31, 2017 , 2016 and 2015 , changes in other operating assets and liabilities as reported in the Consolidated Statements of Cash Flows included the following (in thousands of dollars): December 31, 2017 2016 2015 Decrease (increase) in: Prepaid expenses and other current assets $ 17,160 $ (14,510 ) $ (6,562 ) Other long-term assets (10,349 ) (10,006 ) 13,641 Income tax receivables and deferred income tax assets (33,532 ) 2,395 22,144 (Decrease) increase in: Accrued income taxes and deferred income tax liabilities 35,421 14,879 (27,325 ) Accounts payable and accrued liabilities and other liabilities (14,189 ) 17,297 (29,530 ) Total changes in other operating assets and liabilities $ (5,489 ) $ 10,055 $ (27,632 )

Shareholders' Equity and Divide

Shareholders' Equity and Dividends	12 Months Ended
	Dec. 31, 2017
Shareholders' Equity and Dividends [Abstract]
Shareholders' Equity and Dividends	Shareholders' Equity and Dividends Common Stock —Our common stock is traded on the New York Stock Exchange (the "NYSE") under the symbol BID. Each share of our common stock has a par value of $0.01 per share and is entitled to one vote. As of December 31, 2017 and 2016 , there were 52,461,996 and 52,971,232 shares of our common stock outstanding, respectively. Preferred Stock —We have the authority to issue 50 million shares of no par value preferred stock. No shares of preferred stock were outstanding as of December 31, 2017 and 2016 . Common Stock Repurchase Program —The following table provides information regarding our common stock repurchase program as of and for the years ended December 31, 2017, 2016, and 2015 (in thousands, except for per share data): 2017 2016 2015 Three-Year Total Shares repurchased 961 13,144 3,706 17,811 Aggregate purchase price $ 44,495 $ 359,885 $ 125,000 $ 529,380 Average price per share $ 46.32 $ 27.38 $ 33.73 $ 29.72 On August 6, 2015, the Board of Directors approved an increase of $125 million to our existing share repurchase authorization, which resulted in an updated authorization of $250 million as of that date. On August 13, 2015, we entered into an ASR agreement (the "August 2015 ASR Agreement") pursuant to which we received an initial delivery of 2,667,378 shares of our common stock for an initial purchase price of $125 million . The initial shares received on August 13, 2015 had a value of $100 million , or $37.49 per share. In November 2015, the counterparty to the August 2015 ASR Agreement elected to conclude the agreement, and we received an additional 1,038,280 shares of our common stock. In total, the August 2015 ASR Agreement resulted in the repurchase of 3,705,658 shares of our common stock for an average price of $33.73 per share. On January 21, 2016, the Board of Directors approved a $200 million increase to our share repurchase authorization, which resulted in an updated authorization of $325 million as of that date, and on September 30, 2016, approved an additional share repurchase authorization of $75 million . The share repurchases made in 2016 include open market purchases, purchases made pursuant to a Rule 10b5-1 plan, and purchases made pursuant to an agreement with funds managed by Marcato Capital Management LP ("Marcato") in which we acquired 2,050,000 shares of our common stock from Marcato for an aggregate purchase price of $73.8 million , or $36.00 per share. At the time of this agreement, Marcato owned 8.5% of our outstanding common stock. On August 15, 2017, the Board of Directors approved a $100 million increase to our share repurchase authorization, resulting in an updated share repurchase authorization of $100.03 million at the time. The share repurchases made in 2017 include open market purchases and purchases made pursuant to a Rule 10b5-1 plan. On February 28, 2018, the Board of Directors approved another $100 million increase to our share repurchase authorization, resulting in an updated share repurchase authorization of $195.7 million as of that date. The timing of further share repurchases and the actual amount purchased will depend on a variety of factors including the market price of our common stock, general market and economic conditions, securities law requirements, and other corporate considerations. Repurchases may continue to be made pursuant to plans intended to comply with Rule 10b5-1 under the Exchange Act, which allows us to purchase our shares during periods when we otherwise might be prevented from doing so under insider trading laws or because of self-imposed trading blackout periods. The repurchase authorization does not require the purchase of a specific number of shares and is subject to suspension or termination by our Board of Directors at any time. Quarterly Cash Dividends —The following table summarizes cash dividends declared and paid in each of the quarterly periods in the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars, except per share amounts): 2017 2016 2015 Per Share Amount Per Share Amount Per Share Amount Quarter Ended March 31 $ — $ — $ — $ — $ 0.10 $ 6,944 June 30 — — — — 0.10 6,933 September 30 — — — — 0.10 6,667 December 31 — — — — 0.10 6,563 Total $ — $ — $ — $ — $ 0.40 $ 27,107 On January 21, 2016, our Board of Directors decided to eliminate the $0.10 per share quarterly cash dividend and, instead, allocate the capital to repurchase shares of common stock. Special Dividend —On January 29, 2014, our Board of Directors declared a special dividend of $300 million ( $4.34 per share) that was paid on March 17, 2014. In conjunction with this special dividend, approximately $10 million was accrued for dividend equivalents owed on share-based payments to employees, which was charged to retained earnings. Through December 31, 2017, approximately $9.2 million of such dividends have been paid to employees upon the vesting of the share-based payments, including $2 million , $1.4 million , and $2 million paid in each of March 2017, 2016, and 2015, respectively.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss The following is a summary of the changes in Accumulated Other Comprehensive Loss and the details regarding any reclassification adjustments made during the period January 1, 2015 to December 31, 2017 (in thousands of dollars): 2017 2016 2015 Currency Translation Adjustments Balance at January 1 $ (89,478 ) $ (52,279 ) $ (33,223 ) Other comprehensive income (loss) before reclassifications, net of tax of $1,760, ($13,113), and ($6,345) 14,973 (37,199 ) (18,951 ) Reclassifications from accumulated other comprehensive loss — — (105 ) Other comprehensive income (loss) 14,973 (37,199 ) (19,056 ) Balance at December 31 (74,505 ) (89,478 ) (52,279 ) Cash Flow Hedges Balance at January 1 (3,664 ) (4,306 ) — Other comprehensive income (loss) before reclassifications, net of tax of $888, ($106), and ($3,126) 1,420 (171 ) (4,994 ) Reclassifications from accumulated other comprehensive loss, net of tax of $753, $502, and $430 1,215 813 688 Other comprehensive income (loss) 2,635 642 (4,306 ) Balance at December 31 (1,029 ) (3,664 ) (4,306 ) Net Investment Hedges Balance at January 1 16,618 — — Other comprehensive (loss) income before reclassifications, net of tax of ($1,885), $10,354, and $0 (3,059 ) 16,618 — Other comprehensive (loss) income (3,059 ) 16,618 — Balance at December 31 13,559 16,618 — Defined Benefit Pension Plan Balance at January 1 (13,834 ) (9,619 ) (43,543 ) Currency translation adjustments (1,084 ) 2,300 1,097 Net actuarial gain (loss), net of tax of $2,719, ($1,427), and $6,445 13,277 (6,515 ) 29,363 Other comprehensive income (loss) before reclassifications, net of tax 12,193 (4,215 ) 30,460 Prior service cost amortization, net of tax of ($17), $0, and $73 (80 ) — 291 Actuarial loss amortization, net of tax of $194, $0, and $794 945 — 3,173 Settlement cost, net of tax of $59, $0, and $0 285 — — Reclassifications from accumulated other comprehensive loss, net of tax 1,150 — 3,464 Other comprehensive income (loss) 13,343 (4,215 ) 33,924 Balance at December 31 (491 ) (13,834 ) (9,619 ) Total other comprehensive income (loss) attributable to Sotheby's 27,892 (24,154 ) 10,562 Accumulated other comprehensive loss at December 31 $ (62,466 ) $ (90,358 ) $ (66,204 ) Year Ended December 31, 2017 2016 2015 Cumulative Translation Adjustments Gain upon liquidation of foreign subsidiary $ — $ — $ (105 ) Tax effect — — — Reclassification adjustment, net of tax — — (105 ) Cash Flow Hedges Settlements of interest rate swaps 1,968 1,315 1,118 Tax effect (753 ) (502 ) (430 ) Reclassification adjustments, net of tax 1,215 813 688 Defined Benefit Pension Plan Prior service cost amortization (97 ) — 364 Settlement loss 344 — — Actuarial loss amortization 1,139 — 3,967 Pre-tax total 1,386 — 4,331 Tax effect (236 ) — (867 ) Reclassification adjustments, net of tax 1,150 — 3,464 Total reclassification adjustments, net of tax $ 2,365 $ 813 $ 4,047

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes For the years ended December 31, 2017 , 2016 , and 2015 , the significant components of income tax expense consisted of the following (in thousands of dollars): 2017 2016 2015 Income before taxes: Domestic $ 3,636 $ (38,567 ) $ 11,414 Foreign 138,050 135,301 157,885 Total $ 141,686 $ 96,734 $ 169,299 Income tax expense—current: Domestic $ 24,427 $ 18,443 $ 10,455 State and local 1,492 1,766 5,958 Foreign 27,481 29,904 33,043 Sub-total 53,400 50,113 49,456 Income tax (benefit) expense—deferred: Domestic (34,501 ) (19,114 ) 69,835 State and local 1,285 (1,034 ) 6,378 Foreign 5,231 (4,008 ) 5,476 Sub-total (27,985 ) (24,156 ) 81,689 Total $ 25,415 $ 25,957 $ 131,145 As of December 31, 2017 and 2016 , the components of Deferred Tax Assets and Deferred Tax Liabilities consisted of the following (in thousands of dollars): December 31, 2017 2016 Deferred tax assets: Asset provisions and liabilities $ 4,832 $ 11,512 Inventory writedowns 3,408 10,874 Tax loss and credit carryforwards 3,908 3,708 Difference between book and tax basis of depreciable and amortizable assets 20,218 30,855 Share-based payments and deferred compensation 15,130 26,267 Sub-total 47,496 83,216 Valuation allowance (3,194 ) (2,819 ) Total deferred tax assets 44,302 80,397 Deferred tax liabilities: Difference between book and tax basis of other assets and liabilities 859 1,612 Pension obligations 16,280 9,689 Basis differences in equity method investments 1,269 3,423 Undistributed earnings of foreign subsidiaries 2,571 68,201 Bond redemption costs 2,812 — Total deferred tax liabilities 23,791 82,925 Total net deferred tax assets (liabilities) $ 20,511 $ (2,528 ) As of December 31, 2017 , we had deferred tax assets related to various foreign and state loss and tax credit carryforwards totaling $3.9 million that begin to expire in 2020. As of December 31, 2017 and 2016 , we provided valuation allowances of $3.2 million and $2.8 million , respectively, relating to net operating loss carryforwards. The increase in the valuation allowance in 2017 is due primarily to a change in foreign exchange rates. For the years ended December 31, 2017 , 2016 , and 2015 , our effective income tax rate varied from the U.S. statutory tax rate that was in effect during the periods as follows: 2017 2016 2015 Statutory federal income tax rate 35.0 % 35.0 % 35.0 % State and local taxes, net of federal tax benefit 0.8 % 0.5 % 2.3 % Foreign taxes at rates different from U.S. rates (13.5 %) (25.0 %) (14.9 %) U.S. taxes on foreign earnings 1.2 % 9.9 % 50.5 % Valuation allowance 0.0 % 0.5 % 0.3 % Effect of enacted tax legislation 0.8 % (0.1 %) 2.5 % Changes in tax reserves (4.5 %) 1.6 % 0.0 % Other (1.9 %) 4.4 % 1.8 % Effective income tax rate 17.9 % 26.8 % 77.5 % Our effective income tax rate is 17.9% for the year ended December 31, 2017 , compared to 26.8% in the prior year. The decrease in our effective income tax rate is primarily due to a decrease in U.S. taxes owed on foreign earnings and the reversal in 2017 of a liability for a previously uncertain tax position for which the statute of limitations has expired. These factors are partially offset by a change in the jurisdictional mix of pre-tax earnings, which resulted in a lower portion of our income coming from jurisdictions with a statutory tax rate that is lower than the 35% rate that was in effect in the U.S. during those periods. To a lesser extent, the change in our effective income tax rate between 2017 and 2016 is impacted by provisional net income tax expense of $1.2 million recorded in the fourth quarter of 2017 related to the U.S. Tax Cuts and Jobs Act, as discussed in more detail below. (See Note 17 for additional information on Uncertain Tax Positions.) U.S. Tax Reform —The U.S. Tax Cuts and Jobs Act was enacted into law on December 22, 2017. The Act includes significant changes to the U.S. corporate income tax system that are effective on January 1, 2018, including, among other things, (i) a reduction of the U.S. corporate income tax rate from 35% to 21% , (ii) the transition to a modified territorial tax system from a worldwide tax system, (iii) limitations on the deductibility of interest expense and executive compensation, (iv) the imposition of the Base Erosion Anti-Abuse Tax (“BEAT”), a new minimum tax on international payments meant to reduce the ability of multinational companies to erode the U.S. tax base through deductible payments to related parties, and (v) the creation of two new categories of income: (a) foreign-derived intangible income (“FDII”), which is income derived from the sale of property or services to a foreign person which may be taxed at a rate lower than 21% , and (b) global intangible low taxed income (“GILTI”), which is certain income earned by foreign subsidiaries that must be included in the income of the U.S. shareholder. In addition, the Act imposes a one-time transition tax in the current year on the mandatory redeemed repatriation of certain unremitted foreign earnings as of December 31, 2017. Soon after the Act was enacted into law, the SEC issued SAB 118, which allows companies to record the income tax effects of the Act as a provisional amount based on reasonable estimates for those tax effects. The provisional amount is subject to adjustment as companies complete their analysis of the Act, and collect and prepare the necessary data, and interpret any additional guidance issued by the U.S. Treasury Department, IRS, the FASB, and other standard-setting and regulatory bodies. Any such adjustments may be made within a subsequent measurement period, which should not extend beyond one year from the enactment date. As of December 31, 2017, we have not completed our accounting for the income tax effects of the Act. However, in accordance with SAB 118, we recorded a provisional net income tax expense of approximately $1.2 million in the fourth quarter of 2017 based on reasonable estimates for those tax effects, consisting of the following: • Non-cash income tax expense of $19.8 million due to a reduction in the value of our net deferred tax assets, primarily due to the change in the U.S. corporate tax rate from 35% to 21% and the potential limitation of certain future business deductions; • Income tax expense of $40.4 million to record a liability for the one-time mandatory transition tax on certain unremitted and untaxed earnings of our foreign subsidiaries; and • A non-cash income tax benefit of $59 million to reverse previously recognized deferred tax liabilities related to the earnings of our foreign subsidiaries that were not deemed to be indefinitely reinvested. At December 31, 2017, our Consolidated Balance Sheets reflect a provisional income tax payable of $34.6 million (net of foreign tax credits) primarily for the one-time mandatory transition tax on certain unremitted foreign earnings discussed above. We intend to elect to settle this liability in installments over eight years, as allowed by the Act. Accordingly, we have included approximately $32 million of the liability within long-term liabilities on our Consolidated Balance Sheets as of December 31, 2017. We are still evaluating the effects that BEAT, FDII, GILTI, and other provisions of the Act will have on our Consolidated Financial Statements in future periods. As we complete our analysis of the Act, collect and prepare the necessary data, and interpret any additional guidance issued by the U.S. Treasury Department, the IRS, the FASB, and other standard-setting and regulatory bodies, we may make adjustments to the provisional amounts recorded in the fourth quarter of 2017. These adjustments may impact our provision for income taxes and effective income tax rate in the period in which the adjustments are determined. Our accounting for the income tax effects of the Act will be completed during the measurement period, which should not extend beyond one year from the enactment date. Repatriation of Foreign Earnings —As discussed above, as a result of the Act, in the fourth quarter of 2017, we recorded a provisional tax liability of $40.4 million related to the one-time mandatory transition tax on approximately $460 million of foreign earnings that we have not yet repatriated. In 2018, we expect to repatriate approximately $325 million of these foreign earnings to the U.S., and, as a result, have recorded the related foreign withholding taxes of approximately $3.5 million . Income Tax Payments —Total net income tax payments during 2017 , 2016 , and 2015 were $52.3 million , $32.4 million , and $53.9 million , respectively.

Uncertain Tax Positions

Uncertain Tax Positions	12 Months Ended
	Dec. 31, 2017
Income Tax Uncertainties [Abstract]
Uncertain Tax Positions	Uncertain Tax Positions As of December 31, 2017 , 2016 , and 2015 , the liability for unrecognized tax benefits, excluding interest and penalties, was $13.2 million , $19.5 million , and $22 million , respectively, and is recorded within long-term Accrued Income Taxes on our Consolidated Balance Sheets. As of December 31, 2017 and 2016 , the total amount of unrecognized tax benefits that, if recognized, would favorably affect our effective income tax rate was $4.1 million and $9.3 million , respectively. The table below presents a reconciliation of the beginning and ending balances of the liability for unrecognized tax benefits, excluding interest and penalties, for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars): 2017 2016 2015 Balance at January 1 $ 19,478 $ 22,042 $ 22,798 Increases in unrecognized tax benefits related to the current year 2,512 1,700 2,917 Increases in unrecognized tax benefits related to prior years 2,430 29 2,276 Decreases in unrecognized tax benefits related to prior years (793 ) — (1,973 ) Decreases in unrecognized tax benefits related to settlements (2,075 ) — (437 ) Decreases in unrecognized tax benefits due to the lapse of the applicable statute of limitations (8,378 ) (4,293 ) (3,539 ) Balance at December 31 $ 13,174 $ 19,478 $ 22,042 This net decrease is primarily due to the reversal of tax reserves upon the lapse of the statute of limitations for certain tax years. Also contributing to the decrease in the liability for uncertain tax positions is the settlement of tax audits. These decreases are partially offset by the accrual of tax reserves related to transfer pricing and other U.S. federal and state and non-U.S. matters. The net decreases to the liability for unrecognized tax benefits in 2016 and 2015 were primarily attributable to the expiration of the statutes of limitations for certain tax years, partially offset by the accrual of tax reserves related to transfer pricing and other U.S. federal and state and non-U.S. matters. The net decrease to the liability in 2015 was also due to the closing of tax audits. We recognize interest expense and penalties related to unrecognized tax benefits as a component of Income Tax Expense in our Consolidated Income Statements. During 2017 , 2016 , and 2015 , we recognized a net benefit of $0.9 million , a net expense of $0.3 million , and a net benefit of $0.04 million , respectively, for interest expense and penalties related to unrecognized tax benefits. As of December 31, 2017 , 2016 , and 2015 , the liability for tax-related interest and penalties included in our Consolidated Balance Sheets was $1.2 million , $2.1 million , and $1.8 million , respectively. The net decrease in 2017 is due to the reversal of interest accrued on unrecognized tax benefits, partially offset by the accrual of additional interest on existing unrecognized tax benefits. The net increase in 2016 was due to the accrual of additional interest, partially offset by the reversal of interest accrued on unrecognized tax benefits that were recognized during the year. We are subject to taxation in the U.S. and various state and foreign jurisdictions and, as a result, may be subject to tax audits in these jurisdictions. We are currently under examination by various U.S. state and foreign taxing authorities. The earliest open tax year for the major jurisdictions in which we do business, which includes the U.S. (including various state and local jurisdictions), the U.K., and Hong Kong, is 2011. We believe it is reasonably possible that a decrease of $1.8 million in the balance of unrecognized tax benefits can occur within 12 months of the December 31, 2017 balance sheet date primarily as a result of the expiration of statutes of limitation and the expected settlements of ongoing tax audits.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies Compensation Arrangements —We are party to compensation arrangements with certain senior employees, which expire at various points between March 31, 2018 and December 31, 2022. Such arrangements may provide, among other benefits, for minimum salary levels and for compensation under our incentive compensation programs that is payable only if specified Company and individual goals are attained. Additionally, under certain circumstances, certain of these arrangements provide annual share-based payments, severance payments, and other cash compensation. The aggregate remaining commitment for salaries and other cash compensation related to these compensation arrangements, excluding any participation in our incentive compensation programs, was approximately $16.3 million as of December 31, 2017 . Guarantees of Collection —A guarantee of collection is a commitment to a consignor that, under certain conditions, Sotheby's will fund the payment of the net sale proceeds to the consignor even if the purchaser has not yet made payment. It is not a guarantee that the property will be sold at a certain minimum price. In the event that any item subject to a guarantee of collection is sold and the purchaser does not pay by the settlement date, we are required to pay the consignor the net sale proceeds, but would then take title to the property and have the right to pursue the defaulting buyer and/or reoffer the property at a future sale. In certain limited circumstances, we may also have the right to recover the net sale proceeds from the consignor in the event of an ultimate purchaser default. As of December 31, 2017 , there were no outstanding guarantees of collection. As of February 28, 2017, we had one guarantee of collection outstanding related to property to be offered at auction in the second quarter of 2018 with a pre-sale low estimate of approximately $26 million . Tax Contingencies —We are subject to laws and regulations in many countries involving sales, use, value-added and other indirect taxes which are assessed by various governmental authorities and imposed on certain revenue-producing transactions between us and our clients. The application of these laws and regulations to our unique business and global client base, and the estimation of any related liabilities, is complex and requires a significant amount of judgment. We are generally not responsible for these indirect tax liabilities unless we fail to collect the correct amount of sales, value-added, or other indirect taxes. Failure to collect the correct amount of indirect tax on a transaction may expose us to claims from tax authorities and could require us to record a liability and corresponding charge to our income statement. Legal Contingencies —We become involved in various claims and lawsuits incidental to the ordinary course of our business. We are required to assess the likelihood of any adverse judgments or outcomes related to these legal contingencies, as well as potential ranges of probable or reasonably possible losses. The determination of the amount of any losses to be recorded or disclosed as a result of these contingencies is based on a careful analysis of each individual exposure with, in some cases, the assistance of outside legal counsel. The amount of losses recorded or disclosed for such contingencies may change in the future due to new developments in each matter or a change in settlement strategy. While the impact of any one or more legal claims or proceedings could be material to our operating results in any period, we do not believe that the outcome of any of these pending claims or proceedings (including the matter discussed below), individually or in the aggregate, will have a material adverse effect on our consolidated financial condition. On November 17, 2017, Sotheby’s, together with its London, Geneva and Vienna subsidiaries, and one of its employees (collectively, “the Sotheby’s Parties”), initiated a declaratory judgment action (requête en conciliation) in Switzerland (the “Swiss Action”), at the Tribunal de Première Instance de la République et Canton de Genève, against Dmitry Rybolovlev and various persons and entities affiliated with him. The Sotheby’s Parties’ action seeks a declaration that the Sotheby’s Parties owe no liability or debt to Mr. Rybolovlev and his affiliates in connection with sales of art and related services to entities affiliated with Mr. Yves Bouvier, as discussed in more detail below. The Sotheby’s Parties filed the Swiss Action in response to the stated intent of Mr. Rybolovlev’s counsel to initiate litigation in the U.K. against several of the Sotheby’s Parties. Specifically, on October 27, 2017, counsel for entities affiliated with Mr. Rybolovlev filed papers with the U.S. District Court for the Southern District of New York requesting authority to use documents previously obtained from Sotheby’s pursuant to 28 U.S.C. § 1782. This statute allows parties to conduct discovery in the U.S. for use in foreign legal proceedings. Rybolovlev sought discovery to support a contemplated U.K. proceeding alleging that Sotheby’s and its agents aided and abetted an alleged fraud that Mr. Bouvier allegedly perpetrated against Mr. Rybolovlev and affiliated entities. On December 22, 2017, the District Court in New York approved Mr. Rybolovlev’s request to use Sotheby’s previously disclosed documents both in the contemplated U.K. proceedings, and in the Sotheby’s Parties’ Swiss declaratory judgment proceeding against Mr. Rybolovlev and his affiliates. To date, we are not aware of Mr. Rybolovlev actually filing the threatened U.K. litigation against Sotheby’s, and believe that Geneva is the correct venue for the dispute, that the Lugano Convention effectively precludes Mr. Rybolovlev from sustaining an action in the U.K., and that the Sotheby’s Parties will prevail in the Swiss Action.

Auction Guarantees

Auction Guarantees	12 Months Ended
	Dec. 31, 2017
Auction Guarantees [Abstract]
Auction Guarantees	Auction Guarantees From time-to-time in the ordinary course of our business, we will guarantee to a consignor a minimum sale price in connection with the sale of property at auction (an "auction guarantee"). If the property offered under the auction guarantee sells above the minimum guaranteed price, we are generally entitled to a share of the excess proceeds (the "overage"). In the event that the property sells for less than the minimum guaranteed price, we must perform under the auction guarantee by funding the difference between the sale price at auction and the amount of the auction guarantee (the "shortfall"). The amount of any shortfall recorded in our Consolidated Income Statements is reduced by any auction commissions earned on property sold under the auction guarantee. If any item of property offered under the auction guarantee does not sell, the amount of the auction guarantee must be paid, but we then take ownership of the unsold property and may recover the amount paid through its future sale. In certain limited situations, if the guaranteed property fails to sell at auction or if the purchaser defaults, the consignor has the right to cancel the auction guarantee and retain the property. Depending on the mix of items subject to an auction guarantee, in advance of peak selling seasons, a small number of guaranteed items may represent a substantial portion of the aggregate amount of outstanding auction guarantees. In situations when an item of guaranteed property does not sell and we take ownership of the property, it is recorded as Inventory on our Consolidated Balance Sheets at the lower of its cost (i.e., the amount paid under the auction guarantee) or our estimate of the property's net realizable value (i.e., the expected sale price upon its eventual disposition). The market for fine art, decorative art, and jewelry is not a highly liquid trading market. As a result, the valuation of property acquired as a result of failed auction guarantees is inherently subjective and its realizable value often fluctuates over time. Accordingly, the proceeds ultimately realized on the sale of previously guaranteed property may equal, exceed, or be less than the estimated net realizable value recorded as Inventory on our Consolidated Balance Sheets. We may reduce our financial exposure under auction guarantees through contractual risk and reward sharing arrangements. Such auction guarantee risk and reward sharing arrangements include irrevocable bids and partner sharing arrangements. An irrevocable bid is an arrangement under which a counterparty commits to bid a predetermined price on the guaranteed property. If the irrevocable bid is not the winning bid, the counterparty is generally entitled to receive a share of the auction commission earned on the sale and/or a share of any overage. If the irrevocable bid is the winning bid, the counterparty may receive a fee as compensation for providing the irrevocable bid. This fee may be netted against the counterparty's obligation to pay the full purchase price (i.e., the hammer price plus the applicable buyer's premium). In a partner sharing arrangement, a counterparty commits to fund: (i) a share of the difference between the sale price at auction and the amount of the auction guarantee if the property sells for less than the minimum guaranteed price or (ii) a share of the minimum guaranteed price if the property does not sell while taking ownership of a proportionate share of the unsold property. In exchange for accepting a share of the financial exposure under the auction guarantee, the counterparty in a partner sharing arrangement is generally entitled to receive a share of the auction commission earned if the property sells and/or a share of any overage. The counterparties to our auction guarantee risk and reward sharing arrangements are typically major international art dealers or major art collectors. We could be exposed to losses in the event any of these counterparties do not perform according to the terms of these contractual arrangements. Although irrevocable bid and partner sharing arrangements may be used to reduce the risk associated with auction guarantees, we may also enter into auction guarantees without securing such arrangements. In these circumstances, we could be exposed to deterioration in auction commission margins and/or auction guarantee losses if one or more of the guaranteed items fails to sell at its minimum guaranteed price. Furthermore, in such situations, our liquidity could be reduced. Our credit agreement has a covenant that imposes a $600 million limitation on net outstanding auction guarantees (i.e., the aggregate financial exposure under outstanding auction guarantees less the impact of related risk and reward sharing arrangements). In addition to compliance with this covenant, significant auction guarantees and related risk and reward sharing arrangements are subject to approval by our Board of Directors. As of December 31, 2017 , we had outstanding auction guarantees totaling $28 million . Our financial exposure under these auction guarantees is reduced by irrevocable bids totaling $11.8 million . Each of the outstanding auction guarantees has a minimum guaranteed price that is within or below the range of the pre-sale auction estimates for the underlying property. The property related to these auction guarantees is being offered at auctions during the first and second quarters of 2018. We are obligated under the terms of certain auction guarantees to advance all or a portion of the guaranteed amount prior to auction. As of December 31, 2017 , there were no auction guarantee advances outstanding. As of December 31, 2016, there were $1 million in auction guarantee advances outstanding. As of December 31, 2017 and 2016 , the estimated fair value of our obligation to perform under our outstanding auction guarantees totaled $0.9 million and $0.6 million , respectively, and is recorded within Accounts Payable and Accrued Liabilities on our Consolidated Balance Sheets. As of February 26, 2018, we had outstanding auction guarantees totaling $316.2 million and, as of that date, our financial exposure was reduced by irrevocable bids and partner sharing arrangements totaling $277.6 million . Each of the auction guarantees outstanding as of February 26, 2018, had a minimum guaranteed price that was within or below the range of the pre-sale auction estimates for the underlying property. The property related to these auction guarantees is being offered at auctions in the first and second quarters of 2018. As of February 26, 2018, we have advanced $0.5 million of the total guaranteed amount.

Lease Commitments

Lease Commitments	12 Months Ended
	Dec. 31, 2017
Leases, Operating [Abstract]
Lease Commitments	Lease Commitments We conduct business on premises leased in various locations under long-term operating leases expiring at various dates through 2060. For the years ended December 31, 2017 , 2016 , and 2015 , net rental expense under our operating leases was $18.7 million , $18.4 million , and $17.5 million , respectively, which was recorded within General and Administrative Expenses in our Consolidated Income Statements. Future minimum lease payments due under non-cancellable operating leases in effect at December 31, 2017 were as follows (in thousands of dollars): 2018 $ 19,196 2019 17,086 2020 15,566 2021 11,742 2022 9,425 Thereafter 29,672 Total future minimum lease payments $ 102,687 The future minimum lease payments in the table above exclude future minimum sublease rental receipts of $13.2 million owed to us under noncancellable subleases. In addition to the operating lease payments in the table above, under the terms of certain leases, we are required to pay real estate taxes and utility costs and may be subject to escalations in the amount of future minimum lease payments based on certain contractual provisions.

Share-Based Payments

Share-Based Payments	12 Months Ended
	Dec. 31, 2017
Dividends, Share-based Compensation [Abstract]
Share-Based Payments	Share-Based Payments Share-based payments made to employees include performance-based stock unit awards, market-based stock unit awards, restricted stock units, restricted stock shares, and stock options. Share-based payments are also made to members of our Board of Directors through the issuance of deferred stock units. A description of each of these share-based payments is provided below. For the years ended December 31, 2017 , 2016 , and 2015 , compensation expense for share-based payments made to employees was reflected in the following accounts in our Consolidated Income Statements (in thousands of dollars): 2017 2016 2015 Salaries and related costs $ 23,479 $ 15,935 $ 28,632 Voluntary separation incentive programs (see Note 22) — (719 ) 3,068 CEO separation and transition costs (see Note 23) — — 2,000 Total share-based payment expense (pre-tax) $ 23,479 $ 15,216 $ 33,700 Total share-based payment expense (after-tax) $ 15,555 $ 10,810 $ 22,992 As discussed in Note 1, on January 1, 2017, we adopted ASU 2016-09, Compensation-Stock Compensation: Improvements to Employee Share-Based Payment Accounting . ASU 2016-09 requires, among other things, that all excess tax benefits and deficiencies resulting from the vesting of share-based payments be recorded in the statement of operations, whereas previous guidance generally permitted such items to be recorded in the equity section of the balance sheet provided that an adequate level of previously recorded excess tax benefits existed. This aspect of ASU 2016-09 was adopted on a prospective basis. In 2017, we recognized a $2.7 million excess tax benefit related to share-based payments in our Consolidated Income Statement. This tax benefit represents the amount by which the tax deduction resulting from the vesting of share-based payments and the exercise of stock options during the year exceeded the tax benefit initially recognized in our Consolidated Financial Statements. In 2016, we recognized a ($1.3) million tax shortfall related to share-based payment arrangements. This tax shortfall represents the amount by which the tax deduction resulting from the vesting of share-based payments during the year was less than the tax benefit initially recognized in our Consolidated Financial Statements. As discussed above, prior to the adoption of ASU 2016-09 on January 1, 2017, such tax shortfalls were accounted for as a reduction to previously recorded excess tax benefits related to share-based payments within Additional Paid-in Capital on our Consolidated Balance Sheets. In 2015 , we recognized $1.1 million of excess tax benefits related to share-based payment arrangements. As discussed above, prior to the adoption of ASU 2016-09 on January 1, 2017, such excess tax benefits were recognized on our Consolidated Balance Sheets as an increase to Additional Paid-in Capital. As of December 31, 2017 , unrecognized compensation expense related to the unvested portion of share-based payments to employees was $22.4 million . This compensation expense is expected to be amortized over a weighted-average period of approximately 1.9 years . We do not capitalize compensation expense related to share-based payments to employees. Restricted Stock Unit Plan —The Sotheby's Restricted Stock Unit Plan (as amended and restated, the "Restricted Stock Unit Plan") provides for the issuance of restricted stock units ("RSU's") and restricted shares to employees. Awards made under the Restricted Stock Unit Plan are subject to the approval of the Compensation Committee of our Board of Directors (the "Compensation Committee"). In making awards under the Restricted Stock Unit Plan, the Compensation Committee takes into account the nature of the services rendered by employees, their present and potential future contributions to Sotheby's success, and such other factors as the Compensation Committee in its discretion deems relevant. RSU's and restricted shares issued under the Restricted Stock Unit Plan generally vest evenly over a three -year service period. Prior to vesting, holders of RSU's and restricted shares are entitled to receive non-forfeitable dividend equivalents and dividends, respectively, at the same rate as dividends are paid on our common stock (if and when such dividends are paid). Prior to vesting, holders of RSU's do not have voting rights, while holders of restricted shares have voting rights. RSU's and restricted shares may not be sold, assigned, transferred, pledged or otherwise encumbered until they vest. Performance Share Units (or "PSU's") are RSU's that generally vest over three or four periods, subject to the achievement of certain profitability targets (for awards granted prior to 2016) or certain return on invested capital ("ROIC") targets (for awards granted beginning in 2016). Prior to vesting, holders of PSU's do not have voting rights and are not entitled to receive dividends or dividend equivalents. Dividend equivalents are generally credited to holders of PSU's at the same rate as dividends are paid on our common stock (if and when such dividends are paid), but are only paid for PSU's that vest and become shares of our common stock. PSU's may not be sold, assigned, transferred, pledged or otherwise encumbered until they vest. In 2017, the Compensation Committee approved share-based payment awards with a total grant date fair value of $31.6 million , as follows: • 369,897 PSU's with a grant date fair value of $14.6 million and a single vesting opportunity after a three -year service period. These PSU's provide the recipient with an opportunity to vest in incremental PSU's of up to 100% of the initial award subject to the achievement of certain ROIC targets, for a total maximum vesting opportunity of 200% of the initial award. The maximum number of shares of common stock that may be payable with respect to these awards is 739,794 . • 418,447 RSU's with a grant date fair value of $17 million and annual vesting opportunities over a three -year service period. CEO Share-Based Payment Awards —In the first quarter of 2015, share-based payment awards with a grant date fair value of $16.5 million were granted to Thomas S. Smith, Jr. upon the commencement of his employment as our President and CEO on March 31, 2015. These awards consist of the following: • An inducement award of 158,638 shares of restricted stock with a grant date fair value of $6.5 million , that vesting on various dates between March 4, 2016 and September 1, 2017 to substantially correspond to the times when forfeited opportunities at Mr. Smith's previous employer would otherwise have become eligible to vest. These restricted stock shares were not issued pursuant to the Restricted Stock Unit Plan and have not been registered with the SEC. These shares have voting rights and a non-forfeitable right to dividends. • An inducement award of 47,070 fully-vested RSU's with a grant date fair value of $2 million awarded to Mr. Smith to compensate him for a portion of the annual bonus that he would have received from his previous employer. The common stock shares associated with this award will be distributed in three approximately equal installments on the third, fourth, and fifth anniversaries of the grant date. These RSU's were not issued pursuant to the Restricted Stock Unit Plan and have not been registered with the SEC. These RSU's will be credited with dividend equivalents in the form of additional RSU's if, when, and at the same rate as dividends are paid on our common stock. • An award of 94,140 PSU's under the Restricted Stock Unit Plan with a grant date fair value of $8 million and with a single vesting opportunity after a five -year service period contingent upon the achievement of pre-determined levels of price appreciation in our stock. This award provides opportunities to vest in incremental PSU's up to 350% of the initial award, such that the maximum number of shares that may be payable with respect to this award is 329,490 shares. These PSU's do not have a right to earn dividend equivalents. Subsequent Event: 2018 Share-Based Payment Awards —In 2018, and through February 26, 2018, the Compensation Committee approved share-based payment awards with a total grant date fair value of $29.4 million as follows: • 283,019 PSU's with a grant date fair value of $13.1 million and a single vesting opportunity after a three -year service period. These PSU's provide the recipient with an opportunity to vest in incremental PSU's of up to 100% of the initial awards subject to the achievement of certain ROIC targets, for a total maximum vesting opportunity of 200% of the initial award. The maximum number of shares of common stock that may be payable with respect to these awards is 566,038 . • 346,508 RSU's with a grant date fair value of $16.3 million and annual vesting opportunities over a three -year service period. Summary of Outstanding Share-Based Payment Awards to Employees —For the year ended December 31, 2017 , changes to the number of outstanding RSU's, PSU's, and Restricted Stock shares were as follows (shares in thousands): RSU's, PSU's, and Restricted Weighted Average Grant Date Fair Value Outstanding at January 1, 2017 2,235 $ 36.40 Granted 788 $ 40.12 Vested (838 ) $ 39.20 Canceled (263 ) $ 37.27 Outstanding at December 31, 2017 1,922 $ 36.59 As of December 31, 2017 , 2.4 million shares were available for future awards pursuant to the Restricted Stock Unit Plan. The aggregate fair value of RSU's and PSU's that vested during 2017 , 2016 , and 2015 was $39.7 million , $15.2 million , and $22.9 million , respectively, based on the closing stock price on the dates the shares vested. Stock Options —Stock options issued pursuant to the 1997 Stock Option Plan (the "Stock Option Plan") are exercisable into authorized, but unissued shares of our common stock. Stock options vest evenly over four years and expire 10 years after the date of grant. In the fourth quarter of 2017, the remaining 50,000 stock options that were outstanding under the Stock Option Plan were exercised at an exercise price of $22.11 . The exercised stock options had an intrinsic value of $1.4 million . The resulting $1.1 million in cash proceeds received from the exercise of these stock options were received in January 2018. Also, as a result of the exercise of these stock options, we recognized an excess tax benefit of $0.2 million in our Consolidated Income Statement in the fourth quarter of 2017. As of December 31, 2017 , there were no stock options outstanding or exercisable, and 104,100 shares of common stock were available for the issuance under the Stock Option Plan. Directors Stock Plan —Common stock is issued quarterly under the Sotheby’s Stock Compensation Plan for Non-Employee Directors (as amended and restated, the “Directors Stock Plan”). Directors may elect to receive this compensation in the form of deferred stock units, which are credited in an amount that is equal to the number of shares of common stock the director otherwise would have received. The number of shares of common stock awarded is calculated using the closing price of our common stock on the NYSE on the business day immediately prior to the quarterly grant date. Deferred stock units are held until a director’s termination of service, at which time the units are settled on a one-for-one basis in shares of our common stock on the first day of the calendar month following the date of termination. In 2017, 2016, and 2015, we recognized $1 million , $0.9 million , and $1 million , respectively, within General and Administrative Expenses in our Consolidated Income Statements related to common stock shares awarded under the Directors Stock Plan. As of December 31, 2017 , 168,799 deferred stock units were outstanding under the Directors Stock Plan and 114,869 units were available for future issuance.

Voluntary Separation Incentive

Voluntary Separation Incentive Programs, net	12 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Voluntary Separation Incentive Programs, net	Voluntary Separation Incentive Programs, net On November 13, 2015, we announced a series of regional voluntary separation incentive programs (the "Programs") aimed at reducing headcount and associated compensation costs. The Programs were offered to our employees in jurisdictions where it was practical to do so. Employees who elected to participate in the Programs were accepted only upon approval by management. In the fourth quarter of 2015, we recognized a charge of $36.9 million as a result of the Programs, consisting of $33.8 million in cash severance benefits and $3.1 million in accelerated equity compensation expense related to awards that will continue to vest after termination of employment, subject to our achievement of the underlying profitability targets, when applicable. In 2016, we recognized a net credit of $0.6 million primarily resulting from our quarterly assessment of the likelihood that the performance-based stock units held by participants in the Programs will vest. In 2017, we recognized a credit of $0.2 million as a result of the reversal of the remaining liability related to the Programs following the final payment of severance benefits. Employee transitions and cash severance payments under the Programs have been completed. Restructuring Charges, net On July 16, 2014, our Board of Directors approved a restructuring plan (the "2014 Restructuring Plan") principally impacting our operations in the U.S. and the U.K. The 2014 Restructuring Plan resulted in Restructuring Charges (net) of $14.2 million recognized in 2014, consisting of $13.9 million in employee termination benefits and approximately $0.3 million in lease exit costs. In 2015, we recognized a credit of approximately $1 million in Restructuring Charges (net) as a result of adjustments to the initial accrual for employee termination benefits. The headcount reductions resulting from the 2014 Restructuring Plan were completed in the third quarter of 2015, and the associated liability has been fully settled.

CEO Separation and Transition C

CEO Separation and Transition Costs	12 Months Ended
	Dec. 31, 2017
Compensation Related Costs [Abstract]
CEO Separation and Transition Costs	CEO Separation and Transition Costs In the first quarter of 2015, we recognized CEO Separation and Transition Costs of $4.2 million associated with the hiring of Thomas S. Smith, Jr. as our CEO. This charge principally relates to compensation of $3.1 million owed to Mr. Smith to replace incentive compensation that he expected to receive from his previous employer, consisting of a fully-vested restricted stock unit award with a fair value of $2 million granted on March 31, 2015 and a $1.1 million cash payment that was made in September 2015. The CEO Separation and Transition Costs recognized in the first quarter of 2015 also include approximately $1.1 million in recruitment and other professional fees associated with the CEO hiring process.

Restructuring Charges, net

Restructuring Charges, net	12 Months Ended
	Dec. 31, 2017
Restructuring and Related Activities [Abstract]
Restructuring Charges, net	Voluntary Separation Incentive Programs, net On November 13, 2015, we announced a series of regional voluntary separation incentive programs (the "Programs") aimed at reducing headcount and associated compensation costs. The Programs were offered to our employees in jurisdictions where it was practical to do so. Employees who elected to participate in the Programs were accepted only upon approval by management. In the fourth quarter of 2015, we recognized a charge of $36.9 million as a result of the Programs, consisting of $33.8 million in cash severance benefits and $3.1 million in accelerated equity compensation expense related to awards that will continue to vest after termination of employment, subject to our achievement of the underlying profitability targets, when applicable. In 2016, we recognized a net credit of $0.6 million primarily resulting from our quarterly assessment of the likelihood that the performance-based stock units held by participants in the Programs will vest. In 2017, we recognized a credit of $0.2 million as a result of the reversal of the remaining liability related to the Programs following the final payment of severance benefits. Employee transitions and cash severance payments under the Programs have been completed. Restructuring Charges, net On July 16, 2014, our Board of Directors approved a restructuring plan (the "2014 Restructuring Plan") principally impacting our operations in the U.S. and the U.K. The 2014 Restructuring Plan resulted in Restructuring Charges (net) of $14.2 million recognized in 2014, consisting of $13.9 million in employee termination benefits and approximately $0.3 million in lease exit costs. In 2015, we recognized a credit of approximately $1 million in Restructuring Charges (net) as a result of adjustments to the initial accrual for employee termination benefits. The headcount reductions resulting from the 2014 Restructuring Plan were completed in the third quarter of 2015, and the associated liability has been fully settled.

Earnings Per Share

Earnings Per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings Per Share	Earnings Per Share Basic earnings per share —Basic earnings per share attributable to Sotheby's common shareholders is computed under the two-class method using the weighted average number of common shares outstanding during the period. The two-class method requires that the amount of net income attributable to participating securities be deducted from consolidated net income in the computation of basic earnings per share. In periods with a net loss, the net loss attributable to participating securities is not deducted from consolidated net loss in the computation of basic loss per share as the impact would be anti-dilutive. Our participating securities include unvested restricted stock units and unvested restricted stock shares held by employees, both of which have non-forfeitable rights to dividends. See Note 21 for information on our share-based payment programs. Diluted earnings per share —Diluted earnings per share attributable to Sotheby's common shareholders is computed in a similar manner to basic earnings per share under the two-class method, using the weighted average number of common shares outstanding during the period and, if dilutive, the weighted average number of potential common shares outstanding during the period. Our potential common shares include unvested performance share units held by employees, incremental common shares issuable upon the exercise of employee stock options, and deferred stock units held by members of our Board of Directors. See Note 21 for information on our share-based payment programs. For the years ended December 31, 2017 , 2016 , and 2015 , approximately 1 million potential common shares related to share-based payment awards were excluded from the computation of diluted earnings per share because the financial performance or stock price targets inherent in such awards were not achieved as of the respective balance sheet dates. The table below summarizes the computation of basic and diluted earnings per share for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars, except per share amounts): 2017 2016 2015 Basic: Numerator: Net income attributable to Sotheby's $ 118,796 $ 74,112 $ 43,727 Less: Net income attributable to participating securities 1,765 1,001 354 Net income attributable to Sotheby's common shareholders $ 117,031 $ 73,111 $ 43,373 Denominator: Weighted average common shares outstanding 52,684 57,024 68,121 Basic earnings per share - Sotheby's common shareholders $ 2.22 $ 1.28 $ 0.64 Diluted: Numerator: Net income attributable to Sotheby's 118,796 $ 74,112 $ 43,727 Less: Net income attributable to participating securities 1,765 1,001 354 Net income attributable to Sotheby's common shareholders $ 117,031 $ 73,111 $ 43,373 Denominator: Weighted average common shares outstanding 52,684 57,024 68,121 Weighted average effect of dilutive potential common shares: Performance share units 231 465 438 Deferred stock units 161 149 167 Stock options 25 15 18 Weighted average dilutive potential common shares outstanding 417 629 623 Weighted average diluted shares outstanding 53,101 57,653 68,744 Diluted earnings per share - Sotheby's common shareholders $ 2.20 $ 1.27 $ 0.63 The decrease in weighted average basic and diluted shares outstanding over the three reporting periods is due to common stock repurchases. See Note 14 for additional information on our common stock repurchase program.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	Related Party Transactions From time-to-time, in the ordinary course of business, related parties, such as members of our Board of Directors and management, buy and sell property at our auctions or through private sales brokered by Sotheby's. For the years ended December 31, 2017 , 2016 , and 2015 , we recognized Agency Commissions and Fees of $5.2 million , $4.1 million , and $2.7 million , respectively, related to property sold or purchased by related parties. As of December 31, 2017 and December 31, 2016, Client Payables included amounts owed to related party consignors totaling $0.4 million and $3.6 million , respectively. As of December 31, 2016, Accounts Receivable (net) included $1.8 million , associated with auction purchases made by related parties. As of December 31, 2017, there were no related party Accounts Receivable balances outstanding. On October 3, 2016, we entered into an agreement with funds managed by Marcato Capital Management LP, pursuant to which we purchased 2,050,000 shares of our common stock from Marcato for an aggregate purchase price of $73.8 million , or $36.00 per share. At the time of this agreement, Marcato owned 8.5% of our outstanding common stock. (See Note 14.)

Recently Issued Accounting Stan

Recently Issued Accounting Standards	12 Months Ended
	Dec. 31, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Recently Issued Accounting Standards	Recently Issued Accounting Standards Revenue Recognition —In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers , which introduces a new five-step framework for revenue recognition. The core principal of the standard is that entities should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration for which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 also requires enhanced disclosures regarding the nature, amount, timing, and uncertainty of revenue and cash flows arising from an entity's contracts with customers. On August 12, 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers - Deferral of Effective Date , which defers the effective date of ASU 2014-09 to January 1, 2018 with early adoption beginning January 1, 2017. We will adopt ASU 2014-09 on January 1, 2018 using the full retrospective method. As a result of our adoption of ASU 2014-09, we will change the presentation of certain revenues and expenses currently recorded on a net basis in our Consolidated Income statements. The following table summarizes the anticipated impact of our adoption of ASU 2014-09 for the years ended December 31, 2017 and 2016 (in thousands of dollars): As Currently Reported ASU 2014-09 Adjustment To Be Reported Upon Adoption Year ended December 31, 2017 Agency commissions and fees $ 741,580 $ 68,139 $ 809,719 Total revenues $ 989,389 $ 68,139 $ 1,057,528 Agency direct costs $ 82,142 $ 68,139 $ 150,281 Total expenses $ 819,054 $ 68,139 $ 887,193 Net income attributable to Sotheby's $ 118,796 $ — $ 118,796 Year ended December 31, 2016 Agency commissions and fees $ 671,833 $ 52,565 $ 724,398 Total revenues $ 805,377 $ 52,565 $ 857,942 Agency direct costs $ 73,324 $ 52,565 $ 125,889 Total expenses $ 682,761 $ 52,565 $ 735,326 Net income attributable to Sotheby's $ 74,112 $ — $ 74,112 The adjustments in the table above principally relate to the following items currently reported on a net basis within Agency Commission and Fees that will be reported on a gross basis within Agency Direct Costs upon the adoption of ASU 2014-09: (i) commissions and fees owed to our counterparties in auction guarantee risk and reward sharing arrangements and (ii) commissions owed to third parties who introduce us to consignors or otherwise facilitate the sale of property at auction. To a lesser extent, the adjustments relate to direct cost recoveries (principally for shipping), which are currently reported on a net basis within Agency Direct Costs that will be reported on a gross basis within Agency Commission and Fees upon the adoption of ASU 2014-09. The adoption of ASU 2014-09 will not have an impact on the timing of our revenue recognition. Financial Assets and Liabilities —In January 2016, the FASB issued ASU 2016-01, Financial Instruments-Overall: Recognition and Measurement of Financial Assets and Financial Liabilities. ASU 2016-01 addresses certain aspects of recognition, measurement, presentation, and disclosure of financial instruments, including requirements to measure most equity investments at fair value with changes in fair value recognized in net income, to perform a qualitative assessment of equity investments without readily determinable fair values, and to separately present financial assets and liabilities by measurement category and by type of financial asset on the balance sheet or in the accompanying notes to the financial statements. ASU 2016-01 will be effective for us beginning on January 1, 2018, and will be applied by means of a cumulative effect adjustment to the balance sheet, except for effects related to equity securities without readily determinable values, which will be applied prospectively. The adoption of ASU 2016-01 will not have a material impact on our financial statements. Leases —In February 2016, the FASB issued ASU 2016-02, Leases , which requires long-term lease arrangements to be recognized as assets and liabilities on the balance sheet of the lessee. Under ASU 2016-02, a right-of-use asset and lease obligation will be recorded for all long-term leases, whether operating or financing, while the statement of operations will reflect lease expense for operating leases and interest expense for financing leases. The amendments also require certain new quantitative and qualitative disclosures regarding leasing arrangements. ASU 2016-02 will be effective for us beginning on January 1, 2019. Lessees must apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. Early adoption is permitted. Our assessment of the impact of adopting ASU 2016-02 on our financial statements is ongoing. We are in the process of identifying the population of lease arrangements that are within the scope of ASU 2016-02 and are reviewing the systems and processes that are relevant to the implementation of this standard. Credit Losses —In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments , which amends previously issued guidance regarding the impairment of financial instruments by creating an impairment model that is based on expected losses rather than incurred losses. ASU 2016-13 is effective for us beginning on January 1, 2020. Early adoption is permitted. We are currently assessing the potential impact of adopting ASU 2016-13 on our financial statements. Statement of Cash Flows —In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows , which updates guidance as to how certain cash receipts and cash payments should be presented and classified within the statement of cash flows and is intended to reduce existing diversity in practice. We will adopt ASU 2016-15 using the full retrospective method on January 1, 2018. The adoption of ASU 2016-15 will change the manner in which we report any cash proceeds received from the company-owned life insurance investments held within our deferred compensation plan for certain U.S. employees. Upon adoption, such proceeds will be reported within investing activities, rather than within operating activities. The other aspects of ASU 2016-15 are not expected to have a material impact on our financial statements. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows , which amends ASC 230, Statement of Cash Flows , to add or clarify guidance on the classification and presentation of restricted cash and restricted cash equivalents in the statement of cash flows. In particular, ASU 2016-18 requires that restricted cash and restricted cash equivalents be included within cash and cash equivalents when reconciling the beginning-of-period and end-of-period totals disclosed in the statement of cash flows. Transfers between restricted and unrestricted cash accounts will not be reported within the statement of cash flows. Only restricted cash receipts or payments directly with third parties will be reported in the statement of cash flows as either an operating, investing, or financing activity depending on the nature of the transaction. We will adopt ASU 2016-18 retrospectively on January 1, 2018. Definition of a Business —In January 2017, the FASB issued ASU 2017-01, Clarifying the Definition of a Business , which amends the definition of a business to assist entities with evaluating when a set of transferred assets and activities is a business. ASU 2017-01 is effective for us beginning on January 1, 2018 and must be applied prospectively on or after the effective date. The adoption of ASU 2017-01 will not have a material impact on our financial statements. Goodwill —In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment , which eliminates the requirement to calculate the implied fair value of goodwill to measure a goodwill impairment charge. Instead, entities will record an impairment charge based on the excess of a reporting unit's carrying amount over its fair value. ASU 2017-04 is effective for us beginning on January 1, 2020. Early adoption is permitted. We do not expect the adoption of ASU 2017-04 to have a material impact on our financial statements. Presentation of Pension and Postretirement Costs —In March 2017, the FASB issued ASU 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost , which requires entities to disaggregate the current service cost component from the other components of net pension cost (the "other components") to be included in compensation costs in the income statement and present the other components elsewhere in the statement of operations and outside of income from operations, if that subtotal is presented. In addition, ASU 2017-07 requires entities to disclose the lines in the statement of operations that contain the other components if they are not presented on appropriately described separate lines. ASU 2017-07 is effective for us beginning on January 1, 2018. The adoption of ASU 2017-07 will result in the recording of interest cost, the expected return on plan assets and the amortization of actuarial losses related to the U.K. Pension Plan outside of operating income. Currently, these components of net pension cost (credit) are recorded within Salaries and Related Costs. See Note 8. Stock Compensation —In May 2017, the FASB issued ASU 2017-09, Compensation-Stock Compensation: Scope of Modification Accounting, which amends the scope of modification accounting for share-based payment arrangements. ASU 2017-09 provides guidance on the types of changes to the terms or conditions of share-based payment awards to which an entity would be required to apply modification accounting under ASC 718, Compensation-Stock Compensation . Specifically, an entity would not apply modification accounting if the fair value, vesting conditions, and classification of the awards are the same immediately before and after the modification. We will apply ASU 2017-09 prospectively to any share-based payment awards modified on or after its January 1, 2018 effective date. We do not expect the adoption of ASU 2017-09 to have a material impact on our financial statements. Derivatives —In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities , which provides targeted guidance regarding the accounting for hedging activities to better align an entity’s risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. ASU 2017-12 is effective for us beginning on January 1, 2019. Early adoption is permitted. We are currently assessing the potential impact of adopting ASU 2017-12 on our financial statements. Accumulated Comprehensive Income —On February 14, 2018, the FASB issued ASU 2018-02 to address industry concerns related to the application of ASC 740, Income Taxes , to certain provisions of the U.S. Tax Cuts and Jobs Act. Specifically, some constituents in the banking and insurance industries had expressed concerns about the requirement in ASC 740 that the effect of a change in tax laws or rates on deferred tax assets and liabilities be included in income from continuing operations in the reporting period that contains the enactment date of the change. That guidance applies even in situations in which the tax effects were initially recognized directly in other comprehensive income at the previous rate, resulting in stranded amounts in accumulated other comprehensive income ("AOCI") related to the income tax rate differential. Upon adopting ASU 2018-02, an entity is required to disclose: • Its accounting policy related to releasing income tax effects from AOCI; • Whether it has elected to reclassify, to retained earnings in the statement of stockholders’ equity, the stranded tax effects in AOCI related to the Act; and • If it has elected to reclassify to retained earnings the stranded tax effects in AOCI related to the Act, what the reclassification encompasses (i.e., whether it only includes the change in the federal corporate tax rate or whether it also includes other changes resulting from the Act that affect AOCI). The guidance in ASU 2018-02 is effective for fiscal years beginning after December 15, 2018, including interim periods therein, and early adoption is permitted. An entity will apply this guidance to each period in which the effect of the Act (or portion thereof) is recorded and may apply it either (1) retrospectively as of the date of enactment or (2) as of the beginning of the period of adoption. We are currently evaluating the potential impact of adopting ASU 2018-02 on our financial statements.

Quarterly Results (Unaudited)

Quarterly Results (Unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Quarterly Results (Unaudited)	Quarterly Results (Unaudited) The global art auction market has two principal selling seasons, which generally occur in the second and fourth quarters of the year. In the aggregate, second and fourth quarter Net Auction Sales 1 represented 80% and 82% of our total annual Net Auction Sales in 2017 and 2016 , respectively, with auction commission revenues comprising approximately 66% and 75% of our total revenues, respectively. Accordingly, our financial results are seasonal, with peak revenues and operating income generally occurring in the second and fourth quarters. Consequently, first and third quarter results have historically reflected lower revenues when compared to the second and fourth quarters and, typically, a net loss due to the fixed nature of many of our operating expenses. First Quarter Second Quarter Third Quarter Fourth Quarter (In thousands, except per share data) Year Ended December 31, 2017 Net Auction Sales $ 474,903 $ 1,543,331 $ 286,722 $ 1,511,836 Income Statement Data: Revenues: Agency commissions and fees $ 99,493 $ 276,807 $ 72,650 $ 292,630 Inventory sales 71,377 19,937 81,501 6,167 Finance 12,767 13,359 11,697 13,114 Other 3,900 4,795 5,546 3,649 Total revenues $ 187,537 $ 314,898 $ 171,394 $ 315,560 Operating (loss) income $ (12,854 ) $ 115,398 $ (39,784 ) $ 107,575 Net (loss) income attributable to Sotheby's $ (11,325 ) $ 76,891 $ (23,479 ) $ 76,709 Per Share Amounts: Basic (loss) earnings per share - Sotheby's common shareholders $ (0.21 ) $ 1.44 $ (0.45 ) $ 1.44 Diluted (loss) earnings per share - Sotheby's common shareholders $ (0.21 ) $ 1.43 $ (0.45 ) $ 1.43 Shares Outstanding: Basic 53,016 52,716 52,532 52,471 Diluted 53,016 53,054 52,532 52,853 Year Ended December 31, 2016 Net Auction Sales $ 491,176 $ 1,567,495 $ 160,208 $ 1,337,211 Income Statement Data: Revenues: Agency commissions and fees $ 81,065 $ 273,764 $ 51,285 $ 265,719 Inventory sales 6,794 5,281 24,359 26,429 Finance 14,755 14,750 11,138 12,073 Other 3,917 4,870 4,710 4,468 Total revenues $ 106,531 $ 298,665 $ 91,492 $ 308,689 Operating income (loss) $ (31,989 ) $ 130,083 $ (66,874 ) $ 91,396 Net income (loss) attributable to Sotheby's $ (25,884 ) $ 88,964 $ (23,479 ) $ 65,502 Per Share Amounts: Basic (loss) earnings per share - Sotheby's common shareholders $ (0.41 ) $ 1.54 $ (0.99 ) $ 1.22 Diluted (loss) earnings per share - Sotheby's common shareholders $ (0.41 ) $ 1.52 $ (0.99 ) $ 1.20 Shares Outstanding: Basic 63,022 57,104 55,013 52,956 Diluted 63,022 57,712 55,013 53,685 __________________________________________________________________ 1 Net Auction Sales represents the hammer or sale price of property sold at auction.

Valuation and Qualifying Accoun

Valuation and Qualifying Accounts	12 Months Ended
	Dec. 31, 2017
Valuation and Qualifying Accounts [Abstract]
Valuation and Qualifying Accounts	SCHEDULE II SOTHEBY'S VALUATION AND QUALIFYING ACCOUNTS YEARS ENDED DECEMBER 31, 2017 , 2016 , AND 2015 Column A Column B Column C Column D Column E Description Balance at Beginning of Period Charged to Costs and Expenses Charged to Other Accounts Deductions Balance at End of Period (Thousands of dollars) Valuation reserve deducted in the balance sheet from the asset to which it applies: Receivables: 2017 Allowance for doubtful accounts and credit losses $ 8,940 $ 2,679 $ — $ 119 $ 11,500 2016 Allowance for doubtful accounts and credit losses $ 10,099 $ 928 $ — $ 2,087 $ 8,940 2015 Allowance for doubtful accounts and credit losses $ 8,484 $ 2,607 $ — $ 992 $ 10,099 Deferred tax assets: 2017 Valuation allowance $ 2,819 $ 384 $ — $ 9 $ 3,194 2016 Valuation allowance $ 2,437 $ 526 $ — $ 144 $ 2,819 2015 Valuation allowance $ 2,224 $ 461 $ — $ 248 $ 2,437

Summary of Significant Accoun38

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation —The Consolidated Financial Statements included herein have been prepared in accordance with accounting principles generally accepted in the United States of America ("U.S. GAAP") and pursuant to the rules and regulations of the SEC. In the Consolidated Financial Statements, unless otherwise stated, the terms "art," "works of art," "artwork," and "property" may, as appropriate, refer to authenticated fine art, decorative art, jewelry, wine, or collectibles.
Principles of Consolidation	Principles of Consolidation —The Consolidated Financial Statements include the accounts of our wholly-owned subsidiaries and Sotheby's (Beijing) Auction Co., Ltd. ("Sotheby's Beijing"), a joint venture in which we have a controlling 80% ownership interest. The net loss attributable to the minority owner of Sotheby's Beijing is reported as "Net Loss Attributable to Noncontrolling Interest" in our Consolidated Income Statements and the non-controlling 20% ownership interest is reported as "Noncontrolling Interest" within the Equity section of our Consolidated Balance Sheets. Intercompany transactions and balances among our subsidiaries are eliminated in consolidation. Equity investments through which we may significantly influence, but not control, the investee, are accounted for using the equity method. Under the equity method, our share of investee earnings or losses is recorded in our Consolidated Income Statements within Equity in Earnings of Investees. Our interest in the net assets of these investees is recorded on our Consolidated Balance Sheets within Equity Method Investments. See Note 5 for information related to our equity method investments.
Foreign Currency Translation	Foreign Currency Translation —Assets and liabilities recorded in foreign currencies are translated at the exchange rate on the balance sheet date. Revenues, expenses, gains, and losses recorded in foreign currencies are translated using the monthly average exchange rates prevailing during the period in which they are recognized. Translation adjustments resulting from this process are recorded to Other Comprehensive Income (Loss) and reported on our Consolidated Balance Sheets within Accumulated Other Comprehensive Loss until the subsidiary is sold or liquidated, at which point the adjustments are recognized in Net Income.
Adjustments to Prior Period Presentation	Adjustments to Prior Period Presentation —In March 2016, the Financial Accounting Standards Board (the "FASB") issued Accounting Standards Update ("ASU") 2016-09, Compensation-Stock Compensation: Improvements to Employee Share-Based Payment Accounting. ASU 2016-09 simplifies several aspects of the accounting for and presentation of share-based payment transactions, including the accounting for the related income tax consequences and certain classifications within the statement of cash flows. We adopted ASU 2016-09 on its effective date of January 1, 2017. ASU 2016-09 requires that all excess tax benefits and deficiencies resulting from the vesting of share-based payments be recorded in the income statement, whereas previous guidance generally permitted such items to be recorded in the equity section of the balance sheet provided that an adequate level of previously recorded excess tax benefits existed. We adopted this aspect of ASU 2016-09 on a prospective basis. The adoption of ASU 2016-09 and the vesting of certain share-based payments in 2017 resulted in the recording of a $2.7 million income tax benefit in our Consolidated Income Statements for the year ended December 31, 2017, which decreased our effective income tax rate by approximately 1.8% . Under previous guidance, this income tax benefit would have been recorded as an increase to Additional Paid-In Capital on our Consolidated Balance Sheets. ASU 2016-09 also changed how excess tax benefits resulting from the vesting of share-based payments are presented in the statement of cash flows. ASU 2016-09 requires that such excess tax benefits be classified within Operating Activities along with other income tax cash flows. Under previous guidance, excess tax benefits resulting from the vesting of share-based payments were presented as a cash inflow within Financing Activities and a corresponding cash outflow within Operating Activities. We adopted this aspect of ASU 2016-09 on a retrospective basis. The adoption of ASU 2016-09 and the vesting of certain share-based payments in 2017 resulted in the classification of $2.7 million of excess tax benefits within Operating Activities in our Consolidated Statement of Cash Flows for the year ended December 31, 2017. The retrospective adoption of ASU 2016-09 did not have an effect on our Consolidated Statement of Cash Flows for the year ended December 31, 2016 because no excess tax benefits were recorded in that period.
Restricted Cash	Restricted Cash —Restricted cash may include legally restricted deposits or amounts, cash balances restricted as a result of contracts entered into with third parties or Company statements of intention with regard to particular cash deposits. As of December 31, 2017 and 2016, our Restricted Cash balances include the following (in thousands of dollars): December 31, 2017 2016 Funds deposited with the trustee for the redemption of the 2022 Senior Notes (see Note 9) $ 312,250 $ — Consignor funds held in legally segregated accounts 46,029 53,811 Cash Management Account related to the York Property Mortgage (see Note 9) 3,107 4,635 Other 192 660 Total Restricted Cash $ 361,578 $ 59,106
Valuation of Inventory and Loan Collateral	Valuation of Inventory and Loan Collateral —The art market is not a highly liquid trading market. As a result, the valuation of art is inherently subjective and the realizable value of art often fluctuates over time. In estimating the realizable value of art held in inventory and art pledged as collateral for client loans, we consider the following complex array of factors: (i) whether the property is expected to be offered at auction or sold privately, and the timing of any such sale; (ii) the supply and demand for the property, taking into account current art market conditions, as well as changing trends as to which collecting categories and artists are most sought after; (iii) recent sale prices achieved for comparable items within a particular collecting category and/or by a particular artist; (iv) the state of the global economy and financial markets; and (v) our intent and ability to hold the property in order to maximize its realizable value. Due to the inherent subjectivity involved in estimating the realizable value of art held in inventory and art pledged as collateral for client loans, our estimates of realizable value may prove, with the benefit of hindsight, to be different than the amount ultimately realized upon sale. See below for further discussion of our accounting policies related to Notes Receivable and Inventory.
Accounts Receivable and Allowance for Doubtful Accounts	Accounts Receivable and Allowance for Doubtful Accounts —Accounts Receivable principally includes amounts due from buyers as a result of auction and private sale transactions. The recorded amount reflects the purchase price of the property, including any commissions, as well as any applicable taxes and royalties. The Allowance for Doubtful Accounts principally includes estimated losses associated with situations when we have paid the net sale proceeds to the seller and it is probable that payment will not be collected from the buyer. The Allowance for Doubtful Accounts also includes an estimate of probable losses inherent in the remainder of the Accounts Receivable balance. The amount of the required allowance is based on the facts available to management, including the value of any property held as collateral, and is reevaluated and adjusted as additional facts become known. Based on all available information, we believe that the Allowance for Doubtful Accounts is adequate as of December 31, 2017 ; however, actual losses may ultimately exceed the recorded allowance. As of December 31, 2017 and 2016 , the Allowance for Doubtful Accounts was $8.7 million and $7.7 million , respectively.
Notes Receivable and Allowance for Credit Losses	Notes Receivable and Allowance for Credit Losses —Notes Receivable includes loans made to clients that are secured by artworks. The classification of a loan as current or non-current on our Consolidated Balance Sheets takes into account the contractual maturity date of the loan, as well as the likelihood of renewing the loan on or before its contractual maturity date. The determination of whether a specific loan is impaired and the amount of any required allowance is based on the facts available to management and is reevaluated and adjusted as additional facts become known. A loan is considered to be impaired when we determine that it is probable that a portion of the principal and interest owed by the borrower will not be recovered after taking into account the estimated realizable value of the collateral securing the loan, as well as the ability of the borrower to repay any shortfall between the value of the collateral and the amount of the loan. An allowance is also established for probable losses inherent in the remainder of the loan portfolio based on historical data related to loan losses.
Inventory	Inventory —Inventory consists of artworks that we own and includes the following general categories: (i) items that have been obtained as a result of the failure of guaranteed property to sell at auction , (ii) items that have been purchased opportunistically, including property acquired for sale at auction, and (iii) other objects obtained incidental to the auction process (e.g., as a result of buyer default). See Note 19 for information related to auction guarantees. Inventory is valued on a specific identification basis at the lower of cost or our estimate of realizable value (i.e., the expected sale price upon disposition). If there is evidence that the estimated realizable value of a specific item held in Inventory is less than its carrying value, a writedown is recorded to reflect our revised estimate of realizable va lue. For the years ended December 31, 2017 , 2016 , and 2015 , inventory writedowns totaled $13.6 million , $22.3 million , and $20.1 million , respectively, and were recorded within Cost of Inventory Sales in our Consolidated Income Statements. Although all of the items held in Inventory are available for immediate sale, the timing of eventual sale is difficult to predict due to the high value and unique nature of each item, as well as the cyclical nature of the global art market. We expect that the items held in Inventory will be sold in the ordinary course of our business during the normal operating cycle for such items.
Fixed Assets	Fixed Assets —Fixed Assets are stated at cost less accumulated depreciation and amortization. Depreciation is calculated using the straight-line method over the estimated useful life of the asset. Buildings are depreciated over a useful life of up to 50 years . Building improvements are depreciated over a useful life of up to 20 years . Furniture and fixtures are depreciated over a useful life of up to seven years. Leasehold improvements are amortized using the straight-line method over the lesser of the term of the related lease or the estimated useful life of the improvement. Computer software purchased or developed for internal use consists of the cost of purchased software, as well as direct external and internal software development costs. These costs are amortized on a straight-line basis over the estimated useful life of the software, which is typically between seven to ten years for enterprise systems and three years for other types of software.
Goodwill	Goodwill —Goodwill represents the excess of the purchase price paid over the fair value of net assets acquired in a business combination. Goodwill is not amortized, but is tested annually for impairment at the reporting unit level as of October 31 and between annual tests if indicators of potential impairment exist. These indicators could include a decline in our stock price and market capitalization, a significant change in the outlook for the reporting unit's business, lower than expected operating results, increased competition, legal factors, or the sale or disposition of a significant portion of a reporting unit. An impairment loss is recognized for any amount by which the carrying value of a reporting unit's goodwill exceeds its fair value. The fair value of the reporting units in our Agency segment is determined in reference to a blend of the income and market approaches, and the fair value of our art advisory reporting unit is determined using a discounted cash flow methodology. See Note 7 for information related to Goodwill. The significant assumptions used in the income approach and discounted cash flow approach include (i) forecasted growth rates and (ii) forecasted profitability, both of which are estimated based on consideration of our historical performance and projections of our future performance, and (iii) discount rates that are used to calculate the value of future projected cash flows, which rates are derived based on our estimated weighted average cost of capital. The significant assumptions used in the market approach include selected multiples applied to certain operating metrics. Considerable judgment is necessary to evaluate the impact of operating changes and business initiatives in order to estimate future growth rates and profitability in order to estimate future cash flows and multiples. This is particularly true in a cyclical business, like that of Sotheby's. Future business results could significantly impact the evaluation of our goodwill which could have a material impact on the determination of whether a potential impairment exists and the size of any such impairment.
Intangible Assets	Intangible Assets —Intangible assets are amortized over their estimated useful lives unless the useful life of a particular intangible asset is deemed to be indefinite. If indicators of potential impairment exist, intangible assets with defined useful lives are tested for impairment based on our estimates of undiscounted cash flows and, if impaired, written down to fair value based on either discounted cash flows or appraised values. See Note 7 for information related to Intangible Assets.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets —Long-lived assets are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of the asset may not be recoverable. In such situations, long-lived assets are considered impaired when estimated future cash flows (undiscounted and without interest charges) resulting from the use of the asset and its eventual disposition are less than the asset's carrying amount. In such situations, the asset is written down to the present value of the estimated future cash flows. Factors that are considered when evaluating long-lived assets for impairment include a current expectation that it is more likely than not that the long-lived asset will be sold significantly before the end of its useful life, a significant decrease in the market price of the long-lived asset, and a significant change in the extent or manner in which the long-lived asset is being used.
Valuation of Deferred Tax Assets	Deferred Tax Assets & Liabilities —We follow the liability method of accounting for income taxes under which deferred tax assets and liabilities are recognized, based on enacted tax rates, for the future tax consequences of (i) temporary differences between the tax basis of assets and liabilities and their reported amounts in our consolidated financial statements and (ii) operating loss and tax credit carry-forwards for tax purposes. A valuation allowance is recorded to reduce our deferred tax assets to the amount that is more likely than not to be realized. In assessing the need for the valuation allowance, management considers, among other things, projections of future taxable income and ongoing prudent and feasible tax planning strategies. If we determine that sufficient negative evidence exists (for example, if we experience cumulative three-year losses in a certain jurisdiction), then we will consider recording a valuation allowance against a portion or all of the deferred tax assets in that jurisdiction. If, after recording a valuation allowance, our projections of future taxable income and other positive evidence considered in evaluating the need for a valuation allowance prove, with the benefit of hindsight, to be inaccurate, it could prove to be more difficult to support the realization of our deferred tax assets. As a result, an additional valuation allowance could be required, which would have an adverse impact on our effective income tax rate and results. Conversely, if, after recording a valuation allowance, we determine that sufficient positive evidence exists in the jurisdiction in which the valuation allowance was recorded (for example, if we are no longer in a three-year cumulative loss position in the jurisdiction, and we expect to have future taxable income in that jurisdiction based upon our forecasts and the expected timing of deferred tax asset reversals), we may reverse a portion or all of the valuation allowance in that jurisdiction. In such situations, the adjustment made to the deferred tax asset would have a favorable impact on our effective income tax rate and results in the period such determination was made.
Auction Guarantees	Auction Guarantees —From time-to-time in the ordinary course of our business, we will guarantee to a consignor a minimum sale price in connection with the sale of property at auction (an "auction guarantee"). If the property offered under the auction guarantee sells above the minimum guaranteed price, we are generally entitled to a share of the excess proceeds (the "overage"). In the event that the property sells for less than the minimum guaranteed price, we must perform under the auction guarantee by funding the difference between the sale price at auction and the amount of the auction guarantee (the "shortfall"). The amount of any shortfall recorded in our Consolidated Income Statements is reduced by any auction commissions earned on property sold under the auction guarantee. If any item of property offered under the auction guarantee does not sell, the amount of the auction guarantee must be paid, but we then take ownership of the unsold property and may recover the amount paid through its future sale. In certain limited situations, if the guaranteed property fails to sell at auction or if the purchaser defaults, the consignor has the right to cancel the auction guarantee and retain the property. In situations when an item of guaranteed property does not sell and we take ownership of the property, it is recorded as Inventory on our Consolidated Balance Sheets at the lower of its cost (i.e., the amount paid under the auction guarantee) or our estimate of the property's net realizable value (i.e., the expected sale price upon its eventual disposition). The market for fine art, decorative art, and jewelry is not a highly liquid trading market. As a result, the valuation of property acquired as a result of failed auction guarantees is inherently subjective and its realizable value often fluctuates over time. Accordingly, the proceeds ultimately realized on the sale of previously guaranteed property may equal, exceed, or be less than the estimated net realizable value recorded as Inventory on our Consolidated Balance Sheets. The estimated fair value of our obligation to perform under our auction guarantees is recorded on our Consolidated Balance Sheets within Accounts Payable and Accrued Liabilities. This estimated fair value is based on an analysis of historical loss experience related to auction guarantees and does not include the impact of risk-sharing arrangements that may have mitigated all or a portion of any historical losses.
Financial Instruments	Financial Instruments —Our material financial instruments include (i) Cash and Cash Equivalents; (ii) Restricted Cash; (iii) Notes Receivable; (iv) credit facility borrowings; (v) the mortgage on our headquarters building in New York; (vi) various derivative financial instruments; and (vii) unsecured senior notes. The carrying amounts of Cash and Cash Equivalents, Restricted Cash, Notes Receivable, the mortgage on our headquarters building in New York, and credit facility borrowings do not materially differ from their estimated fair values due to their nature and the variable interest rates associated with each of these financial instruments.
Revenue Recognition	Revenue Recognition (Agency Commissions and Fees) —Through our Agency segment, we accept property on consignment, stimulate buyer interest through professional marketing techniques, and match sellers (also known as consignors) to buyers through the auction or private sale process. Prior to offering a work of art for sale, we perform due diligence activities to authenticate and determine the ownership history of the property being sold. The revenue recognition policy for each of the principal components of Agency Commissions and Fees is described below. (1) Auction Commission Revenues —In our role as auctioneer, we accept property on consignment and match sellers to buyers through the auction process. As compensation for our auction services, we earn a commission from both the buyer ("buyer's premium") and, to a lesser extent, the seller ("seller's commission") (collectively, "auction commission revenue"), both of which are calculated as a percentage of the hammer price of the property sold at auction. On the fall of the auctioneer's hammer, the highest bidder becomes legally obligated to pay the full purchase price, which includes the hammer price of the property purchased plus the buyer's premium, and the seller is legally obligated to relinquish the property in exchange for the hammer price less any seller's commissions. Auction commission revenue is recognized on the date of the auction sale upon the fall of the auctioneer's hammer, which is the point in time when we have substantially accomplished what we must do to be entitled to the benefits represented by the auction commission revenue. Subsequent to the date of the auction sale, our remaining obligations for our auction services relate only to the collection of the purchase price from the buyer and the remittance of the net sale proceeds to the seller. These remaining service obligations are not an essential part of our auction services. Under the standard terms and conditions of our auction sales, we are not obligated to pay the consignor for property that has not been paid for by the buyer. If a buyer defaults on payment, the sale is cancelled, and the property is returned to the consignor. We continually evaluate the collectability of amounts due from individual buyers and only recognize auction commission revenue when the collection of the amount due from the buyer is reasonably assured. If we determine that it is probable that the buyer will default, a cancelled sale is recorded in the period in which that determination is made and the associated Accounts Receivable balance, including our auction commission, is reversed. Our judgments regarding the collectability of Accounts Receivable are based on an assessment of the buyer's payment history, discussions with the buyer, and the value of any property held as security against the buyer's payment obligation. Our judgments with respect to the collectability of amounts due from buyers for auction purchases may prove, with the benefit of hindsight, to be incorrect. Historically, cancelled sales have not been material in relation to the aggregate hammer price of property sold at auction. Auction commission revenues are recorded net of commissions owed to third parties, which are principally the result of situations when the buyer's premium is shared with the consignor or with the counterparty in an auction guarantee risk and reward sharing arrangement (see Note 19 ). Additionally, in certain situations, auction commissions are shared with third parties who introduce us to auction consignors or otherwise facilitate the sale of property at auction. See Note 27, which discusses a change in the presentation of these amounts that will become effective on January 1, 2018 as a the result of the adoption of a new accounting standard related to revenue recognition. (2) Private Sale Commission Revenues —Private sale commission revenues are earned through the direct brokering of purchases and sales of art. Similar to auction sales, the primary service that we provide in a private sale transaction is the matching of the seller to a buyer in a legally binding transaction. Private sales are initiated either by a client wishing to sell property with Sotheby's acting as its exclusive agent in the transaction or a prospective buyer who is interested in purchasing a certain work of art privately. Such arrangements are evidenced by a legally binding agreement between Sotheby's and the seller (a "Seller Agreement"), which outlines the terms of the arrangement, including the desired sale price and the amount or rate of commission to be earned. In certain situations, we may also execute a legally binding agreement with the buyer stipulating the terms of the transaction (a "Buyer Agreement"). The timing of revenue recognition for private sale commissions is evaluated on a case-by-case basis, and in large part, is dependent upon whether a Buyer Agreement has been executed. Additionally, a careful analysis of the individual facts and circumstances is performed for each transaction to fully understand our obligations and performance requirements related to the transaction. In transactions with a Buyer Agreement, our services are performed on the date that the Buyer Agreement is executed. At this point, any remaining service obligations are considered to be inconsequential and perfunctory. Such remaining service obligations normally relate only to the collection of the purchase price from the buyer and the remittance of the net sale proceeds to the seller. These remaining service obligations are not an essential part of the services that we provide in a private sale transaction. In the absence of an executed Buyer Agreement, revenue recognition is deferred until we have performed our substantive service obligations in the transaction and the buyer has paid the full purchase price thereby evidencing the terms of the arrangement. Private sale commission revenues are recorded net of commissions owed to third parties. In certain situations, commissions are shared with third parties who introduce us to consignors who sell property through a private sale transaction. See Note 27, which discusses a change in the presentation of these amounts that will become effective on January 1, 2018 as a the result of the adoption of a new accounting standard related to revenue recognition. (3) Other Agency Commissions and Fees (Net) —Included in Other Agency Commissions and Fees is our share of overage or shortfall related to guaranteed property offered or sold at auction. The overage or shortfall related to guaranteed property is generally recognized in the period in which the property is offered at auction. However, a shortfall is recognized prior to the date of the auction if we determine that a loss related to an auction guarantee is probable. In such situations, we estimate the amount of the loss based on the difference between the amount of the auction guarantee and the expected selling price of the property, including buyer's premium. Also included in Other Agency Commissions and Fees (Net) are commissions and fees earned on sales of art brokered by third parties, fees charged to consignors for property withdrawn prior to auction, and catalogue subscription and advertising revenues. These revenues are recognized in our Consolidated Income Statements when the underlying event occurs or over the period during which we provide the service to our customer. Revenue Recognition (Inventory Sales) —Inventory sales are recognized in the period in which the sale is completed, title to the property passes to the purchaser, and we have fulfilled any other obligations that may be relevant to the transaction, including, but not limited to, delivery of the property. In instances when Inventory is sold at auction, the associated buyer's premium is recorded within Inventory Sales. The carrying value of Inventory sold during a period is recorded within Cost of Inventory Sales. Revenue Recognition (Finance Revenues) —Finance revenues consist principally of interest income earned on Notes Receivable. Such interest income is recognized when earned, based on the amount of the outstanding loan, the applicable interest rate on the loan, and the length of time the loan is outstanding during the period. A non-accrual loan is a loan for which future Finance revenue is not recorded due to our determination that it is probable that future interest on the loan is not collectible. Any cash receipts subsequently received on non-accrual loans are first applied to reduce the recorded principal balance of the loan, with any proceeds in excess of the principal balance then applied to interest owed by the borrower. The recognition of Finance revenue may resume on a non-accrual loan if sufficient additional collateral is provided by the borrower or if we become aware of other circumstances that indicate that it is probable that the borrower will make future interest payments on the loan. See Note 4 for information related to Notes Receivable. Revenue Recognition (Advisory Revenues) —Advisory revenues consist of fees earned from providing art-related advice to certain clients. These arrangements may be evidenced by a legally binding written agreement between us and the client, which outlines the nature of the services to be provided and the amount of fees to be earned. Our advisory services are also sometimes provided on the basis of a verbal agreement with the client. For arrangements with written agreements, advisory revenues are recognized ratably on a straight-line basis over the term of the agreement, provided collectability is reasonably assured. Advisory service arrangements are typically one year in duration. In the absence of a written advisory agreement, revenue recognition is deferred until we have performed our substantive service obligations and the client has made payment for those services thereby evidencing the terms of the arrangement. Advisory revenues are reflected within Other Revenues in our Consolidated Income Statements.
Sales, Use and Value-Added Taxes	Sales, Use and Value-Added Taxes —Sales, use and value-added taxes assessed by governmental authorities that are both imposed on and concurrent with revenue-producing transactions between us and our clients are reported on a net basis within revenues.
Agency Direct Costs	Agency Direct Costs —A large portion of Agency Direct Costs relate to sale marketing expenses such as catalogue production and distribution, advertising and promotion costs, and traveling exhibition costs. Such costs are deferred and recorded on our Consolidated Balance Sheets within Prepaid Expenses and Other Current Assets until the date of the sale when they are recognized in our Consolidated Income Statements.
Cost of Finance Revenues	Cost of Finance Revenues —The Cost of Finance Revenues includes costs related to revolving credit facility borrowings that are used to fund client loans, including interest expense, commitment fees, and the amortization of amendment and arrangement fees.
Salaries and Related Costs	Salaries and Related Costs —Salaries and related costs are not allocated to our cost of revenue, marketing expense, and general and administrative expense line items, as many of our employees perform duties that could be categorized across more than one of these line items.
Share-Based Payments	Share-Based Payments —We grant share-based payment awards as compensation to certain employees. The amount of compensation expense recognized for share-based payments is based, in part, on our estimate of the number of units or shares ultimately expected to vest as a result of employee service. For share-based payment awards that vest annually over a multi-year period of service, compensation expense is amortized over the requisite service period according to a graded vesting schedule. For share-based payment awards that have a single vesting opportunity at the end of a service period, compensation expense is amortized on a straight-line basis over the requisite service period. A substantial portion of the share-based payment awards vest only if we achieve established profitability targets (for awards granted prior to 2016) or certain return on invested capital (or "ROIC") targets (for awards granted beginning in 2016). The amount of compensation expense recognized for such performance-based awards is dependent upon our quarterly assessment of the likelihood of achieving these future profitability or ROIC targets. If, as a result of our assessment, we project that a greater number of performance share units will vest than previously anticipated, a life-to-date adjustment to increase compensation expense is recorded in the period such determination is made. Conversely, if, as a result of our assessment, we project that a lower number of performance share units will vest than previously anticipated, a life-to-date adjustment to decrease compensation expense is recorded in the period such determination is made. Accordingly, if our projections of future performance against these targets prove, with the benefit of hindsight, to be inaccurate, the amount of life-to-date and future compensation expense related to share-based payments could significantly increase or decrease. In 2015, we granted a share-based payment award to Thomas S. Smith, Jr., our President and CEO, with a single vesting opportunity after a five -year service period contingent upon the achievement of pre-determined levels of appreciation related to our common stock. The compensation expense recognized for this share-based payment is based on our estimate of the grant date fair value of the award. In developing this estimate, we considered then-current market conditions, historical data, and any other relevant data. Dividend equivalents related to share-based payments to employees are charged to Retained Earnings.
Use of Estimates	Use of Estimates —The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenues and expenses during the reporting period. Actual results could differ from those estimates.
Segment Reporting	Sotheby's offers collectors the opportunity to connect with and transact in the world's most extraordinary art and luxury goods. Auctioneers since 1744, today we present auctions in ten different salesrooms, including New York, London, Hong Kong and Paris, and Sotheby’s BidNow program allows clients to view all auctions live online and place bids on their mobile devices from anywhere in the world. We also offer collectors a variety of innovative art-related services, including the brokerage of private art sales, private jewelry sales through Sotheby's Diamonds, exclusive private selling exhibitions, art-related financing, and art advisory services, as well as retail wine locations in New York and Hong Kong. Our operations are organized under two segments—the Agency segment and the Finance segment, which does business as and is referred to in this report as Sotheby's Financial Services (or "SFS"). Thomas S. Smith, Jr, Sotheby's CEO, is our chief operating decision maker. Mr. Smith regularly evaluates financial information about each of our segments in deciding how to allocate resources and assess performance. The performance of each segment is measured based on segment income before taxes, which excludes the unallocated items highlighted in the reconciliation below. Through our Agency segment, we accept property on consignment, stimulate buyer interest through professional marketing techniques, and match sellers (also known as consignors) to buyers through the auction or private sale process. Prior to offering a work of art for sale, we perform due diligence activities to authenticate and determine the ownership history of the property being sold. To a much lesser extent, the Agency segment also includes the sale of artworks that are owned by Sotheby's, principally as a consequence of the auction process, as well as our investment in RM Sotheby's, an auction house for investment-quality automobiles. The Agency segment is an aggregation of the auction, private sale, and other related activities conducted by our operating segments in the Americas, Europe, and Asia, which have similar economic characteristics and are similar in their services, customers, and the manner in which their services are provided. SFS is an art financing company that operates as a niche lender with the ability to tailor attractive financing packages for clients who wish to obtain immediate access to liquidity from their art assets. SFS leverages the art expertise of the Agency segment, skill in international law and finance, and access to capital to provide art collectors and dealers with financing secured by their works of art, allowing them to unlock the value in their collections. Art Agency, Partners (“AAP”), which was acquired on January 11, 2016 (see Note 3) and through which we offer art advisory services, provides art collectors with strategic guidance on collection identity and development, acquisitions, short and long-term planning, and provides advice to artists and artists' estates. In addition, from time-to-time, AAP brokers private art sales for its advisory clients. Our advisory services are classified within All Other for segment reporting purposes, along with our retail wine business, brand licensing activities, and the results from certain equity method investments (see Note 5).
Earnings Per Share	Basic earnings per share —Basic earnings per share attributable to Sotheby's common shareholders is computed under the two-class method using the weighted average number of common shares outstanding during the period. The two-class method requires that the amount of net income attributable to participating securities be deducted from consolidated net income in the computation of basic earnings per share. In periods with a net loss, the net loss attributable to participating securities is not deducted from consolidated net loss in the computation of basic loss per share as the impact would be anti-dilutive. Our participating securities include unvested restricted stock units and unvested restricted stock shares held by employees, both of which have non-forfeitable rights to dividends. See Note 21 for information on our share-based payment programs. Diluted earnings per share —Diluted earnings per share attributable to Sotheby's common shareholders is computed in a similar manner to basic earnings per share under the two-class method, using the weighted average number of common shares outstanding during the period and, if dilutive, the weighted average number of potential common shares outstanding during the period. Our potential common shares include unvested performance share units held by employees, incremental common shares issuable upon the exercise of employee stock options, and deferred stock units held by members of our Board of Directors. See Note 21 for information on our share-based payment programs.
Recently Issued Accounting Standards	Recently Issued Accounting Standards Revenue Recognition —In May 2014, the FASB issued ASU 2014-09, Revenue from Contracts with Customers , which introduces a new five-step framework for revenue recognition. The core principal of the standard is that entities should recognize revenue to depict the transfer of promised goods or services to customers in an amount that reflects the consideration for which the entity expects to be entitled in exchange for those goods or services. ASU 2014-09 also requires enhanced disclosures regarding the nature, amount, timing, and uncertainty of revenue and cash flows arising from an entity's contracts with customers. On August 12, 2015, the FASB issued ASU 2015-14, Revenue from Contracts with Customers - Deferral of Effective Date , which defers the effective date of ASU 2014-09 to January 1, 2018 with early adoption beginning January 1, 2017. We will adopt ASU 2014-09 on January 1, 2018 using the full retrospective method. As a result of our adoption of ASU 2014-09, we will change the presentation of certain revenues and expenses currently recorded on a net basis in our Consolidated Income statements. The following table summarizes the anticipated impact of our adoption of ASU 2014-09 for the years ended December 31, 2017 and 2016 (in thousands of dollars): As Currently Reported ASU 2014-09 Adjustment To Be Reported Upon Adoption Year ended December 31, 2017 Agency commissions and fees $ 741,580 $ 68,139 $ 809,719 Total revenues $ 989,389 $ 68,139 $ 1,057,528 Agency direct costs $ 82,142 $ 68,139 $ 150,281 Total expenses $ 819,054 $ 68,139 $ 887,193 Net income attributable to Sotheby's $ 118,796 $ — $ 118,796 Year ended December 31, 2016 Agency commissions and fees $ 671,833 $ 52,565 $ 724,398 Total revenues $ 805,377 $ 52,565 $ 857,942 Agency direct costs $ 73,324 $ 52,565 $ 125,889 Total expenses $ 682,761 $ 52,565 $ 735,326 Net income attributable to Sotheby's $ 74,112 $ — $ 74,112 The adjustments in the table above principally relate to the following items currently reported on a net basis within Agency Commission and Fees that will be reported on a gross basis within Agency Direct Costs upon the adoption of ASU 2014-09: (i) commissions and fees owed to our counterparties in auction guarantee risk and reward sharing arrangements and (ii) commissions owed to third parties who introduce us to consignors or otherwise facilitate the sale of property at auction. To a lesser extent, the adjustments relate to direct cost recoveries (principally for shipping), which are currently reported on a net basis within Agency Direct Costs that will be reported on a gross basis within Agency Commission and Fees upon the adoption of ASU 2014-09. The adoption of ASU 2014-09 will not have an impact on the timing of our revenue recognition. Financial Assets and Liabilities —In January 2016, the FASB issued ASU 2016-01, Financial Instruments-Overall: Recognition and Measurement of Financial Assets and Financial Liabilities. ASU 2016-01 addresses certain aspects of recognition, measurement, presentation, and disclosure of financial instruments, including requirements to measure most equity investments at fair value with changes in fair value recognized in net income, to perform a qualitative assessment of equity investments without readily determinable fair values, and to separately present financial assets and liabilities by measurement category and by type of financial asset on the balance sheet or in the accompanying notes to the financial statements. ASU 2016-01 will be effective for us beginning on January 1, 2018, and will be applied by means of a cumulative effect adjustment to the balance sheet, except for effects related to equity securities without readily determinable values, which will be applied prospectively. The adoption of ASU 2016-01 will not have a material impact on our financial statements. Leases —In February 2016, the FASB issued ASU 2016-02, Leases , which requires long-term lease arrangements to be recognized as assets and liabilities on the balance sheet of the lessee. Under ASU 2016-02, a right-of-use asset and lease obligation will be recorded for all long-term leases, whether operating or financing, while the statement of operations will reflect lease expense for operating leases and interest expense for financing leases. The amendments also require certain new quantitative and qualitative disclosures regarding leasing arrangements. ASU 2016-02 will be effective for us beginning on January 1, 2019. Lessees must apply a modified retrospective transition approach for leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements. Early adoption is permitted. Our assessment of the impact of adopting ASU 2016-02 on our financial statements is ongoing. We are in the process of identifying the population of lease arrangements that are within the scope of ASU 2016-02 and are reviewing the systems and processes that are relevant to the implementation of this standard. Credit Losses —In June 2016, the FASB issued ASU 2016-13, Measurement of Credit Losses on Financial Instruments , which amends previously issued guidance regarding the impairment of financial instruments by creating an impairment model that is based on expected losses rather than incurred losses. ASU 2016-13 is effective for us beginning on January 1, 2020. Early adoption is permitted. We are currently assessing the potential impact of adopting ASU 2016-13 on our financial statements. Statement of Cash Flows —In August 2016, the FASB issued ASU 2016-15, Statement of Cash Flows , which updates guidance as to how certain cash receipts and cash payments should be presented and classified within the statement of cash flows and is intended to reduce existing diversity in practice. We will adopt ASU 2016-15 using the full retrospective method on January 1, 2018. The adoption of ASU 2016-15 will change the manner in which we report any cash proceeds received from the company-owned life insurance investments held within our deferred compensation plan for certain U.S. employees. Upon adoption, such proceeds will be reported within investing activities, rather than within operating activities. The other aspects of ASU 2016-15 are not expected to have a material impact on our financial statements. In November 2016, the FASB issued ASU 2016-18, Statement of Cash Flows , which amends ASC 230, Statement of Cash Flows , to add or clarify guidance on the classification and presentation of restricted cash and restricted cash equivalents in the statement of cash flows. In particular, ASU 2016-18 requires that restricted cash and restricted cash equivalents be included within cash and cash equivalents when reconciling the beginning-of-period and end-of-period totals disclosed in the statement of cash flows. Transfers between restricted and unrestricted cash accounts will not be reported within the statement of cash flows. Only restricted cash receipts or payments directly with third parties will be reported in the statement of cash flows as either an operating, investing, or financing activity depending on the nature of the transaction. We will adopt ASU 2016-18 retrospectively on January 1, 2018. Definition of a Business —In January 2017, the FASB issued ASU 2017-01, Clarifying the Definition of a Business , which amends the definition of a business to assist entities with evaluating when a set of transferred assets and activities is a business. ASU 2017-01 is effective for us beginning on January 1, 2018 and must be applied prospectively on or after the effective date. The adoption of ASU 2017-01 will not have a material impact on our financial statements. Goodwill —In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment , which eliminates the requirement to calculate the implied fair value of goodwill to measure a goodwill impairment charge. Instead, entities will record an impairment charge based on the excess of a reporting unit's carrying amount over its fair value. ASU 2017-04 is effective for us beginning on January 1, 2020. Early adoption is permitted. We do not expect the adoption of ASU 2017-04 to have a material impact on our financial statements. Presentation of Pension and Postretirement Costs —In March 2017, the FASB issued ASU 2017-07, Improving the Presentation of Net Periodic Pension Cost and Net Periodic Postretirement Benefit Cost , which requires entities to disaggregate the current service cost component from the other components of net pension cost (the "other components") to be included in compensation costs in the income statement and present the other components elsewhere in the statement of operations and outside of income from operations, if that subtotal is presented. In addition, ASU 2017-07 requires entities to disclose the lines in the statement of operations that contain the other components if they are not presented on appropriately described separate lines. ASU 2017-07 is effective for us beginning on January 1, 2018. The adoption of ASU 2017-07 will result in the recording of interest cost, the expected return on plan assets and the amortization of actuarial losses related to the U.K. Pension Plan outside of operating income. Currently, these components of net pension cost (credit) are recorded within Salaries and Related Costs. See Note 8. Stock Compensation —In May 2017, the FASB issued ASU 2017-09, Compensation-Stock Compensation: Scope of Modification Accounting, which amends the scope of modification accounting for share-based payment arrangements. ASU 2017-09 provides guidance on the types of changes to the terms or conditions of share-based payment awards to which an entity would be required to apply modification accounting under ASC 718, Compensation-Stock Compensation . Specifically, an entity would not apply modification accounting if the fair value, vesting conditions, and classification of the awards are the same immediately before and after the modification. We will apply ASU 2017-09 prospectively to any share-based payment awards modified on or after its January 1, 2018 effective date. We do not expect the adoption of ASU 2017-09 to have a material impact on our financial statements. Derivatives —In August 2017, the FASB issued ASU 2017-12, Derivatives and Hedging: Targeted Improvements to Accounting for Hedging Activities , which provides targeted guidance regarding the accounting for hedging activities to better align an entity’s risk management activities and financial reporting for hedging relationships through changes to both the designation and measurement guidance for qualifying hedging relationships and the presentation of hedge results. ASU 2017-12 is effective for us beginning on January 1, 2019. Early adoption is permitted. We are currently assessing the potential impact of adopting ASU 2017-12 on our financial statements. Accumulated Comprehensive Income —On February 14, 2018, the FASB issued ASU 2018-02 to address industry concerns related to the application of ASC 740, Income Taxes , to certain provisions of the U.S. Tax Cuts and Jobs Act. Specifically, some constituents in the banking and insurance industries had expressed concerns about the requirement in ASC 740 that the effect of a change in tax laws or rates on deferred tax assets and liabilities be included in income from continuing operations in the reporting period that contains the enactment date of the change. That guidance applies even in situations in which the tax effects were initially recognized directly in other comprehensive income at the previous rate, resulting in stranded amounts in accumulated other comprehensive income ("AOCI") related to the income tax rate differential. Upon adopting ASU 2018-02, an entity is required to disclose: • Its accounting policy related to releasing income tax effects from AOCI; • Whether it has elected to reclassify, to retained earnings in the statement of stockholders’ equity, the stranded tax effects in AOCI related to the Act; and • If it has elected to reclassify to retained earnings the stranded tax effects in AOCI related to the Act, what the reclassification encompasses (i.e., whether it only includes the change in the federal corporate tax rate or whether it also includes other changes resulting from the Act that affect AOCI). The guidance in ASU 2018-02 is effective for fiscal years beginning after December 15, 2018, including interim periods therein, and early adoption is permitted. An entity will apply this guidance to each period in which the effect of the Act (or portion thereof) is recorded and may apply it either (1) retrospectively as of the date of enactment or (2) as of the beginning of the period of adoption. We are currently evaluating the potential impact of adopting ASU 2018-02 on our financial statements.

Summary of Significant Accoun39

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of the effect of adopting ASU 2015-03	The following table summarizes the effect of retrospectively adopting ASU 2016-09 on our Statement of Cash Flows for the year ended December 31, 2015 (in thousands of dollars): Year Ended December 31, 2015 As Previously Reported ASU 2016-09 Adjustments As Adjusted Operating Activities: Adjustments to reconcile net income attributable to Sotheby's to net cash provided by operating activities: Excess tax benefits from share-based payments $ (1,064 ) $ 1,064 $ — Net cash provided by operating activities $ 155,058 $ 1,064 $ 156,122 Financing Activities: Excess tax benefits from share-based payments $ 1,064 $ (1,064 ) $ — Net cash provided by financing activities $ 25,720 $ (1,064 ) $ 24,656 The adoption of the other aspects of ASU 2016-09 did not have a material impact on our Consolidated Financial Statements as of and for years ended December 31, 2017 and 2016. Restricted Cash —Restricted cash may include legally restricted deposits or amounts, cash balances restricted as a result of contracts entered into with third parties or Company statements of intention with regard to particular cash deposits. As of December 31, 2017 and 2016, our Restricted Cash balances include the following (in thousands of dollars): December 31, 2017 2016 Funds deposited with the trustee for the redemption of the 2022 Senior Notes (see Note 9) $ 312,250 $ — Consignor funds held in legally segregated accounts 46,029 53,811 Cash Management Account related to the York Property Mortgage (see Note 9) 3,107 4,635 Other 192 660 Total Restricted Cash $ 361,578 $ 59,106 We will adopt ASU 2014-09 on January 1, 2018 using the full retrospective method. As a result of our adoption of ASU 2014-09, we will change the presentation of certain revenues and expenses currently recorded on a net basis in our Consolidated Income statements. The following table summarizes the anticipated impact of our adoption of ASU 2014-09 for the years ended December 31, 2017 and 2016 (in thousands of dollars): As Currently Reported ASU 2014-09 Adjustment To Be Reported Upon Adoption Year ended December 31, 2017 Agency commissions and fees $ 741,580 $ 68,139 $ 809,719 Total revenues $ 989,389 $ 68,139 $ 1,057,528 Agency direct costs $ 82,142 $ 68,139 $ 150,281 Total expenses $ 819,054 $ 68,139 $ 887,193 Net income attributable to Sotheby's $ 118,796 $ — $ 118,796 Year ended December 31, 2016 Agency commissions and fees $ 671,833 $ 52,565 $ 724,398 Total revenues $ 805,377 $ 52,565 $ 857,942 Agency direct costs $ 73,324 $ 52,565 $ 125,889 Total expenses $ 682,761 $ 52,565 $ 735,326 Net income attributable to Sotheby's $ 74,112 $ — $ 74,112

Segment Reporting (Tables)

Segment Reporting (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Schedule of Segment Information	The following table presents our segment information for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars): Year ended December 31, 2017 Agency SFS All Other Reconciling items Total Revenues $ 907,557 $ 60,105 $ 30,895 $ (9,168 ) (a) $ 989,389 Interest income $ 1,184 $ — $ — $ — $ 1,184 Interest expense $ 32,218 $ — $ — $ — $ 32,218 Depreciation and amortization $ 23,015 $ 244 $ 794 $ — $ 24,053 Segment income before taxes $ 101,203 $ 32,295 $ 10,696 $ (2,508 ) (b) $ 141,686 Year ended December 31, 2016 Revenues $ 726,662 $ 61,234 $ 25,999 $ (8,518 ) (a) $ 805,377 Interest income $ 1,294 $ — $ — $ — $ 1,294 Interest expense $ 30,310 $ — $ — $ — $ 30,310 Depreciation and amortization $ 21,081 $ 119 $ 617 $ — $ 21,817 Segment income (loss) before taxes $ 64,571 (c) $ 35,907 $ (482 ) (c) $ (3,262 ) (b) $ 96,734 Year ended December 31, 2015 Revenues $ 892,030 $ 65,248 $ 18,975 $ (14,759 ) (a) $ 961,494 Interest income $ 1,773 $ 3 $ — $ — $ 1,776 Interest expense $ 32,745 $ — $ — $ — $ 32,745 Depreciation and amortization $ 19,233 $ 124 $ 124 $ — $ 19,481 Segment income before taxes $ 139,942 $ 41,303 $ 10,864 $ (22,810 ) (b) $ 169,299 (a) The reconciling items related to Revenues consist principally of amounts charged by SFS to the Agency segment, including interest and facility fees related to certain loans made to Agency segment clients, as well as fees charged for term loan collateral sold at auction or privately through the Agency segment. (b) The reconciling items related to segment income before taxes are detailed in the table below. (c) Agency segment income before taxes for the year ended December 31, 2016 includes $23.9 million of compensation expense related to an earn-out arrangement with the former principals of AAP. All Other income (loss) before taxes for the year ended December 31, 2016 includes $11.1 million of compensation expense related to this earn-out arrangement. See Note 3 .
Reconciliation of Operating Profit (Loss) from Segments to Consolidated	The table below presents a reconciliation of segment income (loss) before taxes to consolidated income before taxes for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars): 2017 2016 2015 Agency $ 101,203 $ 64,571 $ 139,942 SFS 32,295 35,907 41,303 All Other 10,696 (482 ) 10,864 Segment income before taxes 144,194 99,996 192,109 Unallocated amounts and reconciling items: Leadership transition severance costs (a) — — (13,251 ) CEO separation and transition costs (see Note 23) — — (4,232 ) Equity in earnings of investees (b): (2,508 ) (3,262 ) (5,327 ) Income before taxes $ 141,686 $ 96,734 $ 169,299 (a) In 2015, in conjunction with our leadership transition, we incurred severance costs of $13.3 million associated with the termination of certain executive officers, including our former Chief Financial Officer and former Chief Operating Officer. (b) For segment reporting purposes, our share of earnings related to equity investees is included as part of income before taxes. However, such earnings are reported separately below income before taxes in our Consolidated Income Statements. See Note 5 for information related to our equity method investments.
Schedule of Revenue from External Customers Attributed to Foreign Countries by Geographic Area	The table below presents geographic information about our revenues for the years ended December 31, 2017 , 2016 , and 2015 for all countries which exceeded 5% of total revenues (in thousands of dollars): 2017 2016 2015 United States $ 383,918 $ 367,200 $ 463,129 United Kingdom 229,586 193,721 257,336 Hong Kong and China 223,258 145,885 146,262 Switzerland 95,653 50,003 50,134 France 52,872 42,980 41,803 Other countries 13,270 14,106 17,589 Reconciling item: Intercompany revenue (9,168 ) (8,518 ) (14,759 ) Total $ 989,389 $ 805,377 $ 961,494
Reconciliation of Segment Assets to Consolidated Assets	The table below presents segment assets, as well as a reconciliation of segment assets to consolidated assets as of December 31, 2017 , 2016 , and 2015 (in thousands of dollars): December 31, 2017 2016 2015 Agency $ 2,395,429 $ 1,759,670 $ 2,499,441 SFS 608,713 687,649 721,781 All Other 40,566 42,246 25,178 Total segment assets 3,044,708 2,489,565 3,246,400 Unallocated amounts and reconciling items: Deferred tax assets and income tax receivable 42,599 14,861 16,913 Consolidated assets $ 3,087,307 $ 2,504,426 $ 3,263,313

Acquisition of Art Agency, Pa41

Acquisition of Art Agency, Partners (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Summary of total purchase price allocation to assets acquired and liabilities assumed	The table below summarizes the allocation of the total purchase price paid for AAP to the assets acquired and liabilities assumed (in thousands of dollars): Purchase price: Initial cash consideration $ 50,000 Working capital adjustment 1,189 Total purchase price $ 51,189 Allocation of purchase price: Net working capital acquired $ 1,572 Fixed assets and other long-term assets 173 Goodwill 34,490 Intangible assets - customer relationships (see Note 7) 10,800 Intangible assets - non-compete agreements (see Note 7) 3,060 Deferred tax assets 1,094 Total purchase price $ 51,189

Receivables (Tables)

Receivables (Tables)	12 Months Ended
	Dec. 31, 2017
Accounts and Notes Receivable, Net [Abstract]
Financing Receivable Credit Quality Indicators	The table below provides the aggregate LTV ratio for the SFS loan portfolio as of December 31, 2017 and 2016 (in thousands of dollars): December 31, 2017 2016 Secured loans $ 590,609 $ 675,109 Low auction estimate of collateral $ 1,369,235 $ 1,405,856 Aggregate LTV ratio 43 % 48 % The table below provides the aggregate LTV ratio for secured loans made by SFS with an LTV above 50% as of December 31, 2017 and 2016 (in thousands of dollars): December 31, 2017 2016 Secured loans with an LTV ratio above 50% $ 168,116 $ 270,111 Low auction estimate of collateral related to secured loans with an LTV above 50% $ 269,063 $ 486,973 Aggregate LTV ratio of secured loans with an LTV above 50% 62 % 55 %
Summary Of Other Credit Quality Information Regarding Finance Segment Secured Loans	The table below provides other credit quality information regarding secured loans made by SFS as of December 31, 2017 and 2016 (in thousands of dollars): December 31, 2017 2016 Total secured loans $ 590,609 $ 675,109 Loans past due $ 62,570 $ 90,508 Loans more than 90 days past due $ 56,087 $ 158 Non-accrual loans $ — $ 158 Impaired loans $ — $ — Allowance for credit losses: Allowance for credit losses for impaired loans $ — $ — Allowance for credit losses based on historical data 1,253 1,270 Total allowance for credit losses - secured loans $ 1,253 $ 1,270
Activity Related To Allowance For Credit Losses	For the years ended December 31, 2017 and 2016 , activity related to the Allowance for Credit Losses by segment was as follows (in thousands of dollars): SFS Agency Total Balance as of January 1, 2016 $ 1,458 $ — $ 1,458 Change in loan loss provision based on historical data (188 ) — (188 ) Balance as of December 31, 2016 1,270 — 1,270 Change in loan loss provision based on historical data (17 ) — (17 ) Change in loan loss provision for impaired loans — 1,525 1,525 Balance as of December 31, 2017 $ 1,253 $ 1,525 $ 2,778

Fixed Assets (Tables)

Fixed Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Summary of Fixed Assets	As of December 31, 2017 and 2016 , Fixed Assets consisted of the following (in thousands of dollars): December 31, 2017 2016 Land $ 92,591 $ 92,155 Buildings and building improvements 235,222 230,803 Leasehold improvements 84,504 72,969 Computer hardware and software 77,179 74,744 Furniture, fixtures and equipment 81,031 76,829 Construction in progress 9,492 3,621 Other 1,767 5,257 Sub-total 581,786 556,378 Less: Accumulated depreciation and amortization (229,751 ) (209,196 ) Total Fixed Assets, net $ 352,035 $ 347,182

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	For the years ended December 31, 2017 and 2016, changes in the carrying value of Goodwill were as follows (in thousands of dollars): Year ended December 31, 2017 Year ended December 31, 2016 Agency All Other Total Agency All Other Total Beginning balance as of January 1, $ 43,878 $ 6,151 $ 50,029 $ 13,621 $ — $ 13,621 Goodwill acquired: AAP (see Note 3) — — — 28,339 6,151 34,490 Orion Analytical — — — 2,445 — 2,445 Foreign currency exchange rate changes 518 — 518 (527 ) — (527 ) Ending balance as of December 31, $ 44,396 $ 6,151 $ 50,547 $ 43,878 $ 6,151 $ 50,029
Indefinite-lived Intangible Assets	Intangible Assets —As of December 31, 2017 and 2016 , intangible assets consisted of the following (in thousands of dollars): Amortization Period December 31, 2017 December 31, 2016 Indefinite lived intangible assets: License (a) N/A $ 324 $ 324 Intangible assets subject to amortization: Customer relationships - AAP (see Note 3) 8 years 10,800 10,800 Non-compete agreements - AAP (see Note 3) 6 years 3,060 3,060 Artworks database (b) 10 years 1,200 1,125 Total intangible assets subject to amortization 15,060 14,985 Accumulated amortization (3,892 ) (1,916 ) Total amortizable intangible assets (net) 11,168 13,069 Total intangible assets (net) $ 11,492 $ 13,393 (a) Relates to a license obtained in conjunction with the purchase of a retail wine business in 2008. (b) Relates to a database containing historic information concerning repeat sales of works of art. This database was acquired with the associated business in exchange for an initial cash payment made in the third quarter of 2016 and a subsequent cash payment made in the third quarter of 2017.
Finite-lived Intangible Assets	Intangible Assets —As of December 31, 2017 and 2016 , intangible assets consisted of the following (in thousands of dollars): Amortization Period December 31, 2017 December 31, 2016 Indefinite lived intangible assets: License (a) N/A $ 324 $ 324 Intangible assets subject to amortization: Customer relationships - AAP (see Note 3) 8 years 10,800 10,800 Non-compete agreements - AAP (see Note 3) 6 years 3,060 3,060 Artworks database (b) 10 years 1,200 1,125 Total intangible assets subject to amortization 15,060 14,985 Accumulated amortization (3,892 ) (1,916 ) Total amortizable intangible assets (net) 11,168 13,069 Total intangible assets (net) $ 11,492 $ 13,393 (a) Relates to a license obtained in conjunction with the purchase of a retail wine business in 2008. (b) Relates to a database containing historic information concerning repeat sales of works of art. This database was acquired with the associated business in exchange for an initial cash payment made in the third quarter of 2016 and a subsequent cash payment made in the third quarter of 2017.
Schedule of Finite-Lived Intangible Assets, Future Amortization Expense	The estimated aggregate amortization expense for the remaining useful lives of intangible assets subject to amortization during the five -year period succeeding the December 31, 2017 balance sheet date are as follows (in thousands of dollars): Period Amount 2018 $ 1,980 2019 $ 1,980 2020 $ 1,980 2021 $ 1,980 2022 $ 1,470

Pension Arrangements (Tables)

Pension Arrangements (Tables)	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Trust Assets Related to Deferred Compensation Liability	As of December 31, 2017 and 2016 , the DCP liability was $25.6 million and $25.9 million , respectively, and the assets held in the rabbi trust consisted of the following (in thousands of dollars): December 31, 2017 2016 Company-owned variable life insurance $ 25,567 $ 25,114 Money market mutual fund investments 673 1,599 Total $ 26,240 $ 26,713
Change In Benefit Obligation, Change in Fair Value of Plan Assets, and Funded Status	The table below details the changes in the projected benefit obligation, plan assets, and funded status of the U.K. Pension Plan, as well as the net pension asset recognized on our Consolidated Balance Sheets, as of and for the years ended December 31, 2017 and 2016 (in thousands of dollars): December 31, 2017 2016 Reconciliation of benefit obligation Projected benefit obligation at beginning of year $ 327,619 $ 326,243 Service cost — 1,086 Interest cost 8,053 9,817 Contributions by plan participants — 232 Actuarial (gain) loss (781 ) 64,104 Benefits paid (8,508 ) (12,176 ) Settlement payments (11,880 ) — Foreign currency exchange rate changes 31,373 (61,687 ) Projected benefit obligation at end of year 345,876 327,619 Reconciliation of plan assets Fair value of plan assets at beginning of year 406,195 393,102 Actual return on plan assets 28,827 73,806 Employer contributions — 24,748 Contributions by plan participants — 232 Benefits paid (8,508 ) (12,176 ) Settlement payments (11,880 ) — Foreign currency exchange rate changes 40,068 (73,517 ) Fair value of plan assets at end of year 454,702 406,195 Funded Status Net pension asset $ 108,826 $ 78,576
Pension Benefit Plan	For the years ended December 31, 2017 , 2016 , and 2015 , the components of the net pension (benefit) cost related to the U.K. Pension Plan are as follows (in thousands of dollars): 2017 2016 2015 Service cost $ — $ 1,086 $ 4,497 Interest cost 8,053 9,817 12,923 Prior service cost 60 — — Expected return on plan assets (14,159 ) (17,798 ) (20,174 ) Amortization of actuarial loss 1,139 — 3,967 Amortization of prior service cost (97 ) — 364 Settlement loss 344 — — Net pension (benefit) cost $ (4,660 ) $ (6,895 ) $ 1,577
Benefit Obligation And Net Pension Benefit	As of and for the years ended December 31, 2017 , 2016 , and 2015 , the following assumptions were used in determining the benefit obligation and net pension (benefit) cost related to the U.K. Pension Plan: Benefit Obligation 2017 2016 Weighted average discount rate 2.5% 2.7% Net Pension (Benefit) Cost 2017 2016 2015 Weighted average discount rate N/A N/A 3.5% Weighted average discount rate - service cost N/A 3.8% 3.5% Weighted average discount rate - interest cost 2.4% 3.4% 3.5% Weighted average rate of compensation increase N/A 4.1% 4.1% Weighted average expected long-term rate of return on plan assets 3.8% 5.2% 5.4%
Components of Net Pension Benefits Related to U.K. Pension Plan Assets	The table below presents the fair value of U.K. Pension Plan assets, by investment category, as of December 31, 2017 and 2016 (in thousands of dollars): December 31, 2017 % of Total 2016 % of Total Growth assets $ 104,735 23.0 % $ 217,730 53.6 % Debt securities : Corporate 41,804 9.2 % 35,973 8.9 % Index-linked 219,428 48.3 % 134,972 33.2 % Total debt securities 261,232 57.5 % 170,945 42.1 % Real estate mutual funds 3,233 0.6 % 2,667 0.6 % Cash and cash equivalents 85,502 18.8 % 14,853 3.7 % Total fair value of plan assets $ 454,702 $ 406,195
Fair Value Measurement Information U.K. Pension Plan Assets	The table below provides fair value measurement information for the U.K. Pension Plan assets as of December 31, 2017 (in thousands of dollars): Fair Value Measurements Using: Total Fair Value Quoted Prices in Active Markets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Growth assets $ 104,735 $ 104,735 $ — $ — Debt securities: Corporate 41,804 41,804 — — Index-linked 219,428 219,428 — — Total debt securities 261,232 261,232 — — Real estate mutual funds 3,233 — 3,233 — Cash and cash equivalents 85,502 85,502 — — Total fair value of plan assets $ 454,702 $ 451,469 $ 3,233 $ —
Estimated Future Benefit Payments	Estimated future benefit payments related to the U.K. Pension Plan are as follows (in thousands of dollars): Year Benefit Payments 2018 $ 9,323 2019 $ 8,798 2020 $ 9,729 2021 $ 12,013 2022 $ 11,362 2023 to 2027 $ 66,252

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Instruments [Abstract]
Schedule of Credit Agreements	The following tables summarize information related to the Credit Agreement as of and for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars): As of and for the year ended December 31, 2017 Agency Credit Facility SFS Credit Facility Total Maximum borrowing capacity $ 300,000 $ 800,000 $ 1,100,000 Borrowing base $ 148,299 $ 457,628 $ 605,927 Borrowings outstanding $ — $ 196,500 $ 196,500 Available borrowing capacity (a) $ 148,299 $ 261,128 $ 409,427 Average borrowings outstanding $ — $ 479,367 $ 479,367 Borrowing Costs: Interest $ — (b) $ 15,964 (c) $ 15,964 Fees 2,740 (b) 3,348 (c) 6,088 Total $ 2,740 $ 19,312 $ 22,052 As of and for the year ended December 31, 2016 Agency Credit Facility SFS Credit Facility Total Maximum borrowing capacity $ 300,000 $ 1,035,000 $ 1,335,000 Borrowing base $ 165,443 $ 569,021 $ 734,464 Borrowings outstanding $ — $ 565,000 $ 565,000 Available borrowing capacity (a) $ 165,443 $ 4,021 $ 169,464 Average borrowings outstanding $ — $ 534,433 $ 534,433 Borrowing Costs: Interest $ — (b) $ 14,819 (c) $ 14,819 Fees 2,712 (b) 2,919 (c) 5,631 Total $ 2,712 $ 17,738 $ 20,450 As of and for the year ended December 31, 2015 Agency Credit Facility SFS Credit Facility Total Maximum borrowing capacity $ 300,000 $ 1,035,000 $ 1,335,000 Borrowing base $ 225,642 $ 547,586 $ 773,228 Borrowings outstanding $ — $ 541,500 $ 541,500 Available borrowing capacity (a) $ 225,642 $ 6,086 $ 231,728 Average borrowings outstanding $ — $ 541,004 $ 541,004 Borrowing Costs: Interest $ — (b) $ 14,060 (c) $ 14,060 Fees 2,752 (b) 1,720 (c) 4,472 Total $ 2,752 $ 15,780 $ 18,532 Legend: (a) The available borrowing capacity is calculated as the borrowing base less borrowings outstanding. (b) Borrowing costs related to the Agency Credit Facility, which include interest and fees, are reflected in our Consolidated Income Statements as Interest Expense. (c) Borrowing costs related to the SFS Credit Facility are reflected in our Consolidated Income Statements within Cost of Finance Revenues. For the years ended December 31, 2017 , 2016 , and 2015 , the weighted average cost of borrowings related to the SFS Credit Facility was approximately 4.0% , 3.3% , and 2.9% , respectively. For the year ended December 31, 2017, the Cost of Finance Revenues includes a charge of $0.7 million associated with the reduction in the borrowing capacity of the SFS Credit Facility discussed above.
Schedule of Debt	As of December 31, 2017 and 2016 , Long-Term Debt consisted of the following (in thousands of dollars): December 31, 2017 2016 York Property Mortgage, net of unamortized debt issuance costs of $4,545 and $5,555 $ 270,556 $ 309,212 2022 Senior Notes, net of unamortized debt issuance costs of $2,998 and $3,642 297,002 296,358 2025 Senior Notes, net of unamortized debt issuance costs of $5,623 and $0 394,377 — Less current portion: York Property Mortgage, net of unamortized debt issuance costs of $1,010 and $1,010 (11,930 ) (6,629 ) 2022 Senior Notes, net of unamortized debt issuance costs of $2,998 and $0 (297,002 ) — Total Long-Term Debt, net $ 653,003 $ 598,941
Aggregate Future Principal and Interest Payments	The aggregate future principal, interest, and debt settlement payments, including the $7.9 million call premium owed on the 2022 Senior Notes, due during the five year period after December 31, 2017 are as follows (in thousands of dollars): Year Amount 2018 $ 356,264 2019 $ 42,530 2020 $ 238,963 2021 $ 42,931 2022 $ 247,131
Schedule of Interest Paid	Interest Paid —The table below summarizes interest paid by segment for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars): 2017 2016 2015 Agency $ 33,745 $ 27,793 $ 35,948 SFS 18,062 16,709 17,513 Total $ 51,807 $ 44,502 $ 53,461

Derivative Financial Instrume47

Derivative Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Fair value of derivative financial instruments designated as hedging instruments in the Consolidated Balance Sheet	The following tables present fair value information related to the derivative financial instruments designated as hedging instruments as of December 31, 2017 and 2016 (in thousands of dollars): Assets Liabilities December 31, 2017 Balance Sheet Classification Fair Value Balance Sheet Classification Fair Value Cash Flow Hedges: Interest rate swap Other Current Assets $ 339 N/A $ — Interest rate collar N/A — Other Current Liabilities 666 Interest rate collar N/A — Other Long-Term Liabilities 1,501 Total cash flow hedges 339 — 2,167 Net Investment Hedges: Foreign exchange contracts N/A — Other Current Liabilities 3,756 Total $ 339 $ 5,923 Assets Liabilities December 31, 2016 Balance Sheet Classification Fair Value Balance Sheet Classification Fair Value Cash Flow Hedges: Interest rate swaps Other Current Assets $ 82 Other Current Liabilities $ 163 Interest rate collar N/A — Other Long-Term Liabilities 5,952 Total cash flow hedges 82 6,115 Net Investment Hedges: Foreign exchange contracts Other Current Assets 30,258 N/A — Total $ 30,340 $ 6,115
Effect of derivative financial instruments designated as hedging instruments on Consolidated Income Statements	The following tables summarize the effect of the derivative financial instruments designated as hedging instruments on our Consolidated Income Statements and Consolidated Statements of Comprehensive Income for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars): Gain (Loss) Recognized in Other Comprehensive Income (Loss) - Effective Portion Classification of Gain (Loss) Reclassified from Accumulated Other Comprehensive Loss into Net Income Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Effective Portion Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Ineffective Portion Year Ended December 31, 2017 2016 2015 2017 2016 2015 2017 2016 2015 Cash Flow Hedges: Interest rate swaps $ 201 $ (704 ) $ (802 ) Interest Expense $ 16 $ 813 $ 688 $ — $ — $ — Interest rate collar 1,219 533 (4,192 ) Interest Expense 577 — — — — — Interest rate collar — — — Non-operating income (expense) — — — 622 — — Total cash flow hedges 1,420 (171 ) (4,994 ) 593 813 688 622 — — Net Investment Hedges: Foreign exchange contracts (3,059 ) 16,618 — N/A — — — — — — Total $ (1,639 ) $ 16,447 $ (4,994 ) $ 593 $ 813 $ 688 $ 622 $ — $ —

Supplemental Consolidated Bal48

Supplemental Consolidated Balance Sheet Information (Tables)	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	As of December 31, 2017 and 2016 , Prepaid Expenses and Other Current Assets consisted of the following (in thousands of dollars): December 31, 2017 2016 Prepaid expenses $ 25,418 $ 20,436 Derivative financial instruments (see Note 10) 339 30,340 Insurance recoveries — 19,884 Other 6,253 5,947 Total Prepaid and Other Current Assets $ 32,010 $ 76,607 The reduction in insurance recoveries reflected in the table above is due to claim proceeds received in 2017, as well as the reclassification of certain insurance recoveries to Other Long-Term Assets based on our reassessment of the timing of the anticipated resolution of the matters involved.
Schedule of Other Long-Term Assets	Other Long-Term Assets consisted of the following (in thousands of dollars): December 31, 2017 2016 Defined benefit pension plan asset (see Note 8) $ 108,826 $ 78,576 Equity method investments (see Note 5) 46,905 43,143 Trust assets related to deferred compensation liability (see Note 8) 26,240 26,713 Restricted cash (a) 17,916 1,064 Insurance recoveries 12,242 — Other 15,479 15,928 Total Other Long-Term Assets $ 227,608 $ 165,424 (a) As of December 31, 2017 , restricted cash reflected within Other Long-Term Assets principally relates to $15.3 million of funds held in escrow pending the payment of sale proceeds to a consignor. As of December 31, 2016 , restricted cash reflected within Other Long-Term Assets primarily consisted of segregated cash related to long-term lease arrangements.
Schedule of Other Long-Term Liabilities	Other Long-Term Liabilities consisted of the following (in thousands of dollars): December 31, 2017 2016 Deferred compensation liability (see Note 8) $ 25,614 $ 25,914 Acquisition earn-out consideration (see Note 3) 17,500 26,250 Interest rate collar liability (see Note 10) 1,501 5,952 Other 6,809 6,964 Total Other Long-Term Liabilities $ 51,424 $ 65,080

Supplemental Consolidated Cas49

Supplemental Consolidated Cash Flow Information (Tables)	12 Months Ended
	Dec. 31, 2017
Supplemental Cash Flow Information [Abstract]
Supplemental Consolidated Cash Flow Information	For the years ended December 31, 2017 , 2016 and 2015 , changes in other operating assets and liabilities as reported in the Consolidated Statements of Cash Flows included the following (in thousands of dollars): December 31, 2017 2016 2015 Decrease (increase) in: Prepaid expenses and other current assets $ 17,160 $ (14,510 ) $ (6,562 ) Other long-term assets (10,349 ) (10,006 ) 13,641 Income tax receivables and deferred income tax assets (33,532 ) 2,395 22,144 (Decrease) increase in: Accrued income taxes and deferred income tax liabilities 35,421 14,879 (27,325 ) Accounts payable and accrued liabilities and other liabilities (14,189 ) 17,297 (29,530 ) Total changes in other operating assets and liabilities $ (5,489 ) $ 10,055 $ (27,632 )

Shareholders' Equity and Divi50

Shareholders' Equity and Dividends (Tables)	12 Months Ended
	Dec. 31, 2017
Shareholders' Equity and Dividends [Abstract]
Summary of Common Stock Repurchase Program	The following table provides information regarding our common stock repurchase program as of and for the years ended December 31, 2017, 2016, and 2015 (in thousands, except for per share data): 2017 2016 2015 Three-Year Total Shares repurchased 961 13,144 3,706 17,811 Aggregate purchase price $ 44,495 $ 359,885 $ 125,000 $ 529,380 Average price per share $ 46.32 $ 27.38 $ 33.73 $ 29.72
Schedule of Quarterly Dividends Declared and Paid	The following table summarizes cash dividends declared and paid in each of the quarterly periods in the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars, except per share amounts): 2017 2016 2015 Per Share Amount Per Share Amount Per Share Amount Quarter Ended March 31 $ — $ — $ — $ — $ 0.10 $ 6,944 June 30 — — — — 0.10 6,933 September 30 — — — — 0.10 6,667 December 31 — — — — 0.10 6,563 Total $ — $ — $ — $ — $ 0.40 $ 27,107

Accumulated Other Comprehensi51

Accumulated Other Comprehensive Loss (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Accumulated Other Comprehensive Income (Loss)	The following is a summary of the changes in Accumulated Other Comprehensive Loss and the details regarding any reclassification adjustments made during the period January 1, 2015 to December 31, 2017 (in thousands of dollars): 2017 2016 2015 Currency Translation Adjustments Balance at January 1 $ (89,478 ) $ (52,279 ) $ (33,223 ) Other comprehensive income (loss) before reclassifications, net of tax of $1,760, ($13,113), and ($6,345) 14,973 (37,199 ) (18,951 ) Reclassifications from accumulated other comprehensive loss — — (105 ) Other comprehensive income (loss) 14,973 (37,199 ) (19,056 ) Balance at December 31 (74,505 ) (89,478 ) (52,279 ) Cash Flow Hedges Balance at January 1 (3,664 ) (4,306 ) — Other comprehensive income (loss) before reclassifications, net of tax of $888, ($106), and ($3,126) 1,420 (171 ) (4,994 ) Reclassifications from accumulated other comprehensive loss, net of tax of $753, $502, and $430 1,215 813 688 Other comprehensive income (loss) 2,635 642 (4,306 ) Balance at December 31 (1,029 ) (3,664 ) (4,306 ) Net Investment Hedges Balance at January 1 16,618 — — Other comprehensive (loss) income before reclassifications, net of tax of ($1,885), $10,354, and $0 (3,059 ) 16,618 — Other comprehensive (loss) income (3,059 ) 16,618 — Balance at December 31 13,559 16,618 — Defined Benefit Pension Plan Balance at January 1 (13,834 ) (9,619 ) (43,543 ) Currency translation adjustments (1,084 ) 2,300 1,097 Net actuarial gain (loss), net of tax of $2,719, ($1,427), and $6,445 13,277 (6,515 ) 29,363 Other comprehensive income (loss) before reclassifications, net of tax 12,193 (4,215 ) 30,460 Prior service cost amortization, net of tax of ($17), $0, and $73 (80 ) — 291 Actuarial loss amortization, net of tax of $194, $0, and $794 945 — 3,173 Settlement cost, net of tax of $59, $0, and $0 285 — — Reclassifications from accumulated other comprehensive loss, net of tax 1,150 — 3,464 Other comprehensive income (loss) 13,343 (4,215 ) 33,924 Balance at December 31 (491 ) (13,834 ) (9,619 ) Total other comprehensive income (loss) attributable to Sotheby's 27,892 (24,154 ) 10,562 Accumulated other comprehensive loss at December 31 $ (62,466 ) $ (90,358 ) $ (66,204 )
Reclassification out of Accumulated Other Comprehensive Income (Loss)	Year Ended December 31, 2017 2016 2015 Cumulative Translation Adjustments Gain upon liquidation of foreign subsidiary $ — $ — $ (105 ) Tax effect — — — Reclassification adjustment, net of tax — — (105 ) Cash Flow Hedges Settlements of interest rate swaps 1,968 1,315 1,118 Tax effect (753 ) (502 ) (430 ) Reclassification adjustments, net of tax 1,215 813 688 Defined Benefit Pension Plan Prior service cost amortization (97 ) — 364 Settlement loss 344 — — Actuarial loss amortization 1,139 — 3,967 Pre-tax total 1,386 — 4,331 Tax effect (236 ) — (867 ) Reclassification adjustments, net of tax 1,150 — 3,464 Total reclassification adjustments, net of tax $ 2,365 $ 813 $ 4,047

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Components of Income Tax Expense (Benefit)	For the years ended December 31, 2017 , 2016 , and 2015 , the significant components of income tax expense consisted of the following (in thousands of dollars): 2017 2016 2015 Income before taxes: Domestic $ 3,636 $ (38,567 ) $ 11,414 Foreign 138,050 135,301 157,885 Total $ 141,686 $ 96,734 $ 169,299 Income tax expense—current: Domestic $ 24,427 $ 18,443 $ 10,455 State and local 1,492 1,766 5,958 Foreign 27,481 29,904 33,043 Sub-total 53,400 50,113 49,456 Income tax (benefit) expense—deferred: Domestic (34,501 ) (19,114 ) 69,835 State and local 1,285 (1,034 ) 6,378 Foreign 5,231 (4,008 ) 5,476 Sub-total (27,985 ) (24,156 ) 81,689 Total $ 25,415 $ 25,957 $ 131,145
Schedule of Deferred Tax Assets and Liabilities	As of December 31, 2017 and 2016 , the components of Deferred Tax Assets and Deferred Tax Liabilities consisted of the following (in thousands of dollars): December 31, 2017 2016 Deferred tax assets: Asset provisions and liabilities $ 4,832 $ 11,512 Inventory writedowns 3,408 10,874 Tax loss and credit carryforwards 3,908 3,708 Difference between book and tax basis of depreciable and amortizable assets 20,218 30,855 Share-based payments and deferred compensation 15,130 26,267 Sub-total 47,496 83,216 Valuation allowance (3,194 ) (2,819 ) Total deferred tax assets 44,302 80,397 Deferred tax liabilities: Difference between book and tax basis of other assets and liabilities 859 1,612 Pension obligations 16,280 9,689 Basis differences in equity method investments 1,269 3,423 Undistributed earnings of foreign subsidiaries 2,571 68,201 Bond redemption costs 2,812 — Total deferred tax liabilities 23,791 82,925 Total net deferred tax assets (liabilities) $ 20,511 $ (2,528 )
Schedule of Effective Income Tax Rate Reconciliation	For the years ended December 31, 2017 , 2016 , and 2015 , our effective income tax rate varied from the U.S. statutory tax rate that was in effect during the periods as follows: 2017 2016 2015 Statutory federal income tax rate 35.0 % 35.0 % 35.0 % State and local taxes, net of federal tax benefit 0.8 % 0.5 % 2.3 % Foreign taxes at rates different from U.S. rates (13.5 %) (25.0 %) (14.9 %) U.S. taxes on foreign earnings 1.2 % 9.9 % 50.5 % Valuation allowance 0.0 % 0.5 % 0.3 % Effect of enacted tax legislation 0.8 % (0.1 %) 2.5 % Changes in tax reserves (4.5 %) 1.6 % 0.0 % Other (1.9 %) 4.4 % 1.8 % Effective income tax rate 17.9 % 26.8 % 77.5 %

Uncertain Tax Positions (Tables

Uncertain Tax Positions (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Uncertainties [Abstract]
Summary of Income Tax Contingencies	The table below presents a reconciliation of the beginning and ending balances of the liability for unrecognized tax benefits, excluding interest and penalties, for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars): 2017 2016 2015 Balance at January 1 $ 19,478 $ 22,042 $ 22,798 Increases in unrecognized tax benefits related to the current year 2,512 1,700 2,917 Increases in unrecognized tax benefits related to prior years 2,430 29 2,276 Decreases in unrecognized tax benefits related to prior years (793 ) — (1,973 ) Decreases in unrecognized tax benefits related to settlements (2,075 ) — (437 ) Decreases in unrecognized tax benefits due to the lapse of the applicable statute of limitations (8,378 ) (4,293 ) (3,539 ) Balance at December 31 $ 13,174 $ 19,478 $ 22,042

Lease Commitments Lease Commitm

Lease Commitments Lease Commitments (Tables)	12 Months Ended
	Dec. 31, 2017
Leases, Operating [Abstract]
Schedule of Future Minimum Rental Payments for Operating Leases	Future minimum lease payments due under non-cancellable operating leases in effect at December 31, 2017 were as follows (in thousands of dollars): 2018 $ 19,196 2019 17,086 2020 15,566 2021 11,742 2022 9,425 Thereafter 29,672 Total future minimum lease payments $ 102,687

Share-Based Payments (Tables)

Share-Based Payments (Tables)	12 Months Ended
	Dec. 31, 2017
Dividends, Share-based Compensation [Abstract]
Compensation Expense Related to Share-Based Payments	For the years ended December 31, 2017 , 2016 , and 2015 , compensation expense for share-based payments made to employees was reflected in the following accounts in our Consolidated Income Statements (in thousands of dollars): 2017 2016 2015 Salaries and related costs $ 23,479 $ 15,935 $ 28,632 Voluntary separation incentive programs (see Note 22) — (719 ) 3,068 CEO separation and transition costs (see Note 23) — — 2,000 Total share-based payment expense (pre-tax) $ 23,479 $ 15,216 $ 33,700 Total share-based payment expense (after-tax) $ 15,555 $ 10,810 $ 22,992
Changes in Number of Outstanding Restricted Stock, RSU's and PSU's	For the year ended December 31, 2017 , changes to the number of outstanding RSU's, PSU's, and Restricted Stock shares were as follows (shares in thousands): RSU's, PSU's, and Restricted Weighted Average Grant Date Fair Value Outstanding at January 1, 2017 2,235 $ 36.40 Granted 788 $ 40.12 Vested (838 ) $ 39.20 Canceled (263 ) $ 37.27 Outstanding at December 31, 2017 1,922 $ 36.59

Earnings Per Share (Tables)

Earnings Per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Computation of Basic and Diluted Earnings Per Share	The table below summarizes the computation of basic and diluted earnings per share for the years ended December 31, 2017 , 2016 , and 2015 (in thousands of dollars, except per share amounts): 2017 2016 2015 Basic: Numerator: Net income attributable to Sotheby's $ 118,796 $ 74,112 $ 43,727 Less: Net income attributable to participating securities 1,765 1,001 354 Net income attributable to Sotheby's common shareholders $ 117,031 $ 73,111 $ 43,373 Denominator: Weighted average common shares outstanding 52,684 57,024 68,121 Basic earnings per share - Sotheby's common shareholders $ 2.22 $ 1.28 $ 0.64 Diluted: Numerator: Net income attributable to Sotheby's 118,796 $ 74,112 $ 43,727 Less: Net income attributable to participating securities 1,765 1,001 354 Net income attributable to Sotheby's common shareholders $ 117,031 $ 73,111 $ 43,373 Denominator: Weighted average common shares outstanding 52,684 57,024 68,121 Weighted average effect of dilutive potential common shares: Performance share units 231 465 438 Deferred stock units 161 149 167 Stock options 25 15 18 Weighted average dilutive potential common shares outstanding 417 629 623 Weighted average diluted shares outstanding 53,101 57,653 68,744 Diluted earnings per share - Sotheby's common shareholders $ 2.20 $ 1.27 $ 0.63

Recently Issued Accounting St57

Recently Issued Accounting Standards (Tables)	12 Months Ended
	Dec. 31, 2017
New Accounting Pronouncements and Changes in Accounting Principles [Abstract]
Summary of the effect of adopting ASU 2014-09	The following table summarizes the effect of retrospectively adopting ASU 2016-09 on our Statement of Cash Flows for the year ended December 31, 2015 (in thousands of dollars): Year Ended December 31, 2015 As Previously Reported ASU 2016-09 Adjustments As Adjusted Operating Activities: Adjustments to reconcile net income attributable to Sotheby's to net cash provided by operating activities: Excess tax benefits from share-based payments $ (1,064 ) $ 1,064 $ — Net cash provided by operating activities $ 155,058 $ 1,064 $ 156,122 Financing Activities: Excess tax benefits from share-based payments $ 1,064 $ (1,064 ) $ — Net cash provided by financing activities $ 25,720 $ (1,064 ) $ 24,656 The adoption of the other aspects of ASU 2016-09 did not have a material impact on our Consolidated Financial Statements as of and for years ended December 31, 2017 and 2016. Restricted Cash —Restricted cash may include legally restricted deposits or amounts, cash balances restricted as a result of contracts entered into with third parties or Company statements of intention with regard to particular cash deposits. As of December 31, 2017 and 2016, our Restricted Cash balances include the following (in thousands of dollars): December 31, 2017 2016 Funds deposited with the trustee for the redemption of the 2022 Senior Notes (see Note 9) $ 312,250 $ — Consignor funds held in legally segregated accounts 46,029 53,811 Cash Management Account related to the York Property Mortgage (see Note 9) 3,107 4,635 Other 192 660 Total Restricted Cash $ 361,578 $ 59,106 We will adopt ASU 2014-09 on January 1, 2018 using the full retrospective method. As a result of our adoption of ASU 2014-09, we will change the presentation of certain revenues and expenses currently recorded on a net basis in our Consolidated Income statements. The following table summarizes the anticipated impact of our adoption of ASU 2014-09 for the years ended December 31, 2017 and 2016 (in thousands of dollars): As Currently Reported ASU 2014-09 Adjustment To Be Reported Upon Adoption Year ended December 31, 2017 Agency commissions and fees $ 741,580 $ 68,139 $ 809,719 Total revenues $ 989,389 $ 68,139 $ 1,057,528 Agency direct costs $ 82,142 $ 68,139 $ 150,281 Total expenses $ 819,054 $ 68,139 $ 887,193 Net income attributable to Sotheby's $ 118,796 $ — $ 118,796 Year ended December 31, 2016 Agency commissions and fees $ 671,833 $ 52,565 $ 724,398 Total revenues $ 805,377 $ 52,565 $ 857,942 Agency direct costs $ 73,324 $ 52,565 $ 125,889 Total expenses $ 682,761 $ 52,565 $ 735,326 Net income attributable to Sotheby's $ 74,112 $ — $ 74,112

Quarterly Results (Unaudited) (

Quarterly Results (Unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Schedule of Quarterly Results	First Quarter Second Quarter Third Quarter Fourth Quarter (In thousands, except per share data) Year Ended December 31, 2017 Net Auction Sales $ 474,903 $ 1,543,331 $ 286,722 $ 1,511,836 Income Statement Data: Revenues: Agency commissions and fees $ 99,493 $ 276,807 $ 72,650 $ 292,630 Inventory sales 71,377 19,937 81,501 6,167 Finance 12,767 13,359 11,697 13,114 Other 3,900 4,795 5,546 3,649 Total revenues $ 187,537 $ 314,898 $ 171,394 $ 315,560 Operating (loss) income $ (12,854 ) $ 115,398 $ (39,784 ) $ 107,575 Net (loss) income attributable to Sotheby's $ (11,325 ) $ 76,891 $ (23,479 ) $ 76,709 Per Share Amounts: Basic (loss) earnings per share - Sotheby's common shareholders $ (0.21 ) $ 1.44 $ (0.45 ) $ 1.44 Diluted (loss) earnings per share - Sotheby's common shareholders $ (0.21 ) $ 1.43 $ (0.45 ) $ 1.43 Shares Outstanding: Basic 53,016 52,716 52,532 52,471 Diluted 53,016 53,054 52,532 52,853 Year Ended December 31, 2016 Net Auction Sales $ 491,176 $ 1,567,495 $ 160,208 $ 1,337,211 Income Statement Data: Revenues: Agency commissions and fees $ 81,065 $ 273,764 $ 51,285 $ 265,719 Inventory sales 6,794 5,281 24,359 26,429 Finance 14,755 14,750 11,138 12,073 Other 3,917 4,870 4,710 4,468 Total revenues $ 106,531 $ 298,665 $ 91,492 $ 308,689 Operating income (loss) $ (31,989 ) $ 130,083 $ (66,874 ) $ 91,396 Net income (loss) attributable to Sotheby's $ (25,884 ) $ 88,964 $ (23,479 ) $ 65,502 Per Share Amounts: Basic (loss) earnings per share - Sotheby's common shareholders $ (0.41 ) $ 1.54 $ (0.99 ) $ 1.22 Diluted (loss) earnings per share - Sotheby's common shareholders $ (0.41 ) $ 1.52 $ (0.99 ) $ 1.20 Shares Outstanding: Basic 63,022 57,104 55,013 52,956 Diluted 63,022 57,712 55,013 53,685 __________________________________________________________________ 1 Net Auction Sales represents the hammer or sale price of property sold at auction.

Summary of Significant Accoun59

Summary of Significant Accounting Policies (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Tax Cuts And Jobs Act Of 2017, Incomplete Accounting, Provisional Income Tax Expense (Benefit)	$ 1.2
Principles of Consolidation
Noncontrolling ownership interest percentage	20.00%	20.00%
Accounts Receivable, Net Accounts Receivable and Allowance for Doubtful Accounts
Allowance for doubtful accounts receivable	$ 8.7	$ 8.7	$ 7.7
Inventory
Inventory writedown		$ 13.6	$ 22.3	$ 20.1
New CEO 2015 Agreement | Performance Shares
Share-Based Payments
Award service period				5 years
Building
Fixed Assets
Fixed assets useful life		50 years
Building improvements
Fixed Assets
Fixed assets useful life		20 years
Furniture and fixtures
Fixed Assets
Fixed assets useful life		7 years
Enterprise systems | Minimum
Fixed Assets
Fixed assets useful life		7 years
Enterprise systems | Maximum
Fixed Assets
Fixed assets useful life		10 years
Computer software
Fixed Assets
Fixed assets useful life		3 years
Sotheby's Beijing
Principles of Consolidation
Controlling ownership interest percentage by parent	80.00%	80.00%

Summary of Significant Accoun60

Summary of Significant Accounting Policies (Adoption of Accounting Standards Update) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefits from share-based payments			$ 0
Net cash provided by operating activities	$ 366,185	$ 158,370	156,122
Excess tax benefits from share-based payments			0
Net cash provided by financing activities	(383,971)	(356,275)	24,656
Total Restricted Cash	361,578	59,106
Funds deposited with the trustee for the redemption of the 2022 Senior Notes
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Restricted Cash	312,250	0
Consignor funds held in legally segregated accounts
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Restricted Cash	46,029	53,811
Cash Management Account related to York Property Mortgage
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Restricted Cash	3,107	4,635
Other
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Total Restricted Cash	192	$ 660
ASU 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefits from share-based payments	$ 2,700		1,064
Excess tax benefit, percent	1.80%
Net cash provided by operating activities			1,064
Excess tax benefits from share-based payments			(1,064)
Net cash provided by financing activities			(1,064)
As Previously Reported
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefits from share-based payments			(1,064)
Net cash provided by operating activities			155,058
Excess tax benefits from share-based payments			1,064
Net cash provided by financing activities			$ 25,720

Segment Reporting (Narrative) (

Segment Reporting (Narrative) (Details)	12 Months Ended
	Dec. 31, 2017segment
Segment Reporting [Abstract]
Number of operating segments (in segment)	2
Revenue from external customers as a percentage of total revenue	5.00%

Segment Reporting (Schedule Of

Segment Reporting (Schedule Of Revenue And (Loss) Income Before Taxes by Segment) (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Revenues	$ 315,560,000	$ 171,394,000	$ 314,898,000	$ 187,537,000	$ 308,689,000	$ 91,492,000	$ 298,665,000	$ 106,531,000	$ 989,389,000	$ 805,377,000	$ 961,494,000
Interest income									1,184,000	1,294,000	1,776,000
Interest expense									32,218,000	30,310,000	32,745,000
Depreciation and amortization									24,053,000	21,817,000	19,481,000
Segment income before taxes									141,686,000	96,734,000	169,299,000
Art Agency, Partners | Earn Out
Segment Reporting Information [Line Items]
Compensation expense related to earn-out arrangement										35,000,000
Reconciling items
Segment Reporting Information [Line Items]
Revenues									(9,168,000)	(8,518,000)	(14,759,000)
Interest income									0	0	0
Interest expense									0	0	0
Depreciation and amortization									0	0	0
Segment income before taxes									(2,508,000)	(3,262,000)	(22,810,000)
Agency | Art Agency, Partners | Earn Out
Segment Reporting Information [Line Items]
Compensation expense related to earn-out arrangement										23,900,000
Agency | Operating Segments
Segment Reporting Information [Line Items]
Revenues									907,557,000	726,662,000	892,030,000
Interest income									1,184,000	1,294,000	1,773,000
Interest expense									32,218,000	30,310,000	32,745,000
Depreciation and amortization									23,015,000	21,081,000	19,233,000
Segment income before taxes									101,203,000	64,571,000	139,942,000
SFS | Operating Segments
Segment Reporting Information [Line Items]
Revenues									60,105,000	61,234,000	65,248,000
Interest income									0	0	3,000
Interest expense									0	0	0
Depreciation and amortization									244,000	119,000	124,000
Segment income before taxes									32,295,000	35,907,000	41,303,000
All Other | Art Agency, Partners | Earn Out
Segment Reporting Information [Line Items]
Compensation expense related to earn-out arrangement										11,100,000
All Other | Operating Segments
Segment Reporting Information [Line Items]
Revenues									30,895,000	25,999,000	18,975,000
Interest income									0	0	0
Interest expense									0	0	0
Depreciation and amortization									794,000	617,000	124,000
Segment income before taxes									$ 10,696,000	$ (482,000)	$ 10,864,000

Segment Reporting (Reconciliati

Segment Reporting (Reconciliation Of Segment (Loss) Income Before Taxes) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
CEO separation and transition costs	$ (4,200)	$ 0	$ 0	$ (4,232)
Equity in earnings of investees		(2,508)	(3,262)	(5,327)
Income before taxes		141,686	96,734	169,299
Operating Segments
Segment Reporting Information [Line Items]
Segment (loss) income before taxes		144,194	99,996	192,109
Reconciling items
Segment Reporting Information [Line Items]
Leadership transition severance costs		0	0	(13,251)
CEO separation and transition costs		0	0	(4,232)
Equity in earnings of investees		(2,508)	(3,262)	(5,327)
Income before taxes		(2,508)	(3,262)	(22,810)
Agency | Operating Segments
Segment Reporting Information [Line Items]
Segment (loss) income before taxes		101,203	64,571	139,942
Income before taxes		101,203	64,571	139,942
SFS | Operating Segments
Segment Reporting Information [Line Items]
Segment (loss) income before taxes		32,295	35,907	41,303
Income before taxes		32,295	35,907	41,303
All Other | Operating Segments
Segment Reporting Information [Line Items]
Segment (loss) income before taxes		10,696	(482)	10,864
Income before taxes		$ 10,696	$ (482)	$ 10,864

Segment Reporting (Schedule o64

Segment Reporting (Schedule of Revenues by Geographic Region) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues	$ 315,560	$ 171,394	$ 314,898	$ 187,537	$ 308,689	$ 91,492	$ 298,665	$ 106,531	$ 989,389	$ 805,377	$ 961,494
Intercompany revenue
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									(9,168)	(8,518)	(14,759)
United States | Reportable Geographical Components
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									383,918	367,200	463,129
United Kingdom | Reportable Geographical Components
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									229,586	193,721	257,336
Hong Kong and China | Reportable Geographical Components
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									223,258	145,885	146,262
Switzerland | Reportable Geographical Components
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									95,653	50,003	50,134
France | Reportable Geographical Components
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									52,872	42,980	41,803
Other countries | Reportable Geographical Components
Revenues from External Customers and Long-Lived Assets [Line Items]
Total revenues									$ 13,270	$ 14,106	$ 17,589

Segment Reporting (Reconcilia65

Segment Reporting (Reconciliation Of Segment Assets To Consolidated Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Assets	$ 3,087,307	$ 2,504,426	$ 3,263,313
Operating Segments
Segment Reporting Information [Line Items]
Assets	3,044,708	2,489,565	3,246,400
Operating Segments | Agency
Segment Reporting Information [Line Items]
Assets	2,395,429	1,759,670	2,499,441
Operating Segments | SFS
Segment Reporting Information [Line Items]
Assets	608,713	687,649	721,781
Operating Segments | All Other
Segment Reporting Information [Line Items]
Assets	40,566	42,246	25,178
Reconciling items
Segment Reporting Information [Line Items]
Assets	$ 42,599	$ 14,861	$ 16,913

Acquisition of Art Agency, Pa66

Acquisition of Art Agency, Partners (Details)	Jan. 11, 2016USD ($)	Jun. 30, 2017USD ($)	Mar. 31, 2017USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)annual_incremental_payment
Business Acquisition [Line Items]
Acquisition earn-out consideration (see Note 3)						$ 17,500,000	$ 26,250,000
Allocation of purchase price:
Goodwill					$ 13,621,000	50,547,000	50,029,000
Period over which goodwill is tax deductible		15 years
Agency
Allocation of purchase price:
Goodwill					13,621,000	44,396,000	43,878,000
All Other
Allocation of purchase price:
Goodwill					0	6,151,000	6,151,000
Art Agency, Partners
Purchase price:
Initial cash consideration	$ 50,000,000
Working capital adjustment	1,189,000
Total purchase price	51,189,000
Allocation of purchase price:
Net working capital acquired	1,572,000
Fixed assets and other long-term assets	173,000
Goodwill	34,490,000
Deferred tax assets	1,094,000
Total purchase price	51,189,000
Goodwill acquired						0	34,490,000
Transaction costs	800,000
Art Agency, Partners | General and Administrative Expenses
Allocation of purchase price:
Transaction expenses				$ (200,000)	$ (600,000)
Art Agency, Partners | Agency
Allocation of purchase price:
Goodwill acquired		$ 28,300,000				0	28,339,000
Art Agency, Partners | All Other
Allocation of purchase price:
Goodwill acquired		$ 6,200,000				0	6,151,000
Art Agency, Partners | Customer relationships
Allocation of purchase price:
Intangible assets	10,800,000
Art Agency, Partners | Employment contracts
Allocation of purchase price:
Intangible assets	$ 3,060,000
Art Agency, Partners | Former Owner
Business Acquisition [Line Items]
Employment agreement term	5 years
Non-compete and non-solicit covenants period after employment agreement	12 months
Art Agency, Partners | Earn Out
Business Acquisition [Line Items]
Compensation expense related to earn-out arrangement							$ 35,000,000
Settlement period for earn-out payments	4 years
Number of annual incremental payments | annual_incremental_payment							4
Maximum annual payments under contingent earn-out agreement			$ 8,750,000
Contingent consideration, liability, current						8,750,000
Acquisition earn-out consideration (see Note 3)						$ 17,500,000
Art Agency, Partners | Earn Out | Agency
Business Acquisition [Line Items]
Compensation expense related to earn-out arrangement							$ 23,900,000
Art Agency, Partners | Earn Out | All Other
Business Acquisition [Line Items]
Compensation expense related to earn-out arrangement							$ 11,100,000

Receivables (Narrative) (Detail

Receivables (Narrative) (Details) - USD ($)	2 Months Ended	3 Months Ended	12 Months Ended
	Feb. 26, 2018	Jun. 30, 2013	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Accounts, Notes, Loans and Financing Receivable [Line Items]
Maximum buyer payment term			30 days
Consignor payment term			35 days
Buyer receivables classified within other long term assets			$ 2,700,000	$ 7,500,000
Net accounts receivable			795,239,000	433,614,000
Balance of secured loan to refinance auction or private sale receivable			54,400,000	88,700,000
Secured loan issued to refinance auction or private sale receivable			6,500,000	13,300,000
Total secured loans			$ 590,609,000	675,109,000
Loan-to-value ratio			50.00%
Borrowing percentage			85.00%
Loans past due			$ 62,570,000	90,508,000
Loans more than 90 days past due accruing interest			56,087,000	158,000
Accrual of interest			1,800,000
Loans investment			49,500,000
Non-accrual loans			0	158,000
Impaired loans			0	0
Unfunded lending commitment to extend additional credit			51,800,000
Loan balance			2,778,000	1,270,000	$ 1,458,000
Unsecured loan				2,100,000
Equity interest sold		$ 4,300,000
Proceeds from the sale of equity method investment			2,125,000	325,000	275,000
Subsequent Event
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan To Value (LTV) Ratio	100.00%
Loans investment	$ 15,500,000
Non-accrual loans	47,700,000
Collateral sold	10,200,000
Proceeds from sale of collateral	23,800,000
Auction guarantee advances outstanding	$ 500,000
Unsecured Loan
Accounts, Notes, Loans and Financing Receivable [Line Items]
Equity interest sold		3,500,000
Up-front Payment Arrangement
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from the sale of equity method investment		$ 800,000
SFS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Finance segment secured loans			590,609,000	675,109,000
Collections of loans originally issued to refinance auction or private sale			$ 40,800,000	$ 33,400,000
Loan-to-value ratio			43.00%	48.00%
Loan To Value (LTV) Ratio			60.00%
Low auction estimate of collateral			$ 1,369,235,000	$ 1,405,856,000
Impaired loans			0	0
Loan balance			1,253,000	1,270,000	1,458,000
Agency
Accounts, Notes, Loans and Financing Receivable [Line Items]
Collections of loans originally issued to refinance auction or private sale			5,000,000	16,300,000
Total secured loans				3,800,000
Low auction estimate of collateral			3,100,000	3,100,000
Auction guarantee advances outstanding			0	1,000,000
Loan balance			1,525,000	0	$ 0
Unsecured loan			$ 2,100,000
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan-to-value ratio			50.00%
Loan To Value (LTV) Ratio			51.00%
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan To Value (LTV) Ratio			60.00%
Accounts Rec, Consignor Paid
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net accounts receivable			$ 92,100,000	90,100,000
Transfer Of Possession Without Payment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net accounts receivable			$ 53,800,000	$ 76,300,000
Notes receivable past due
Accounts, Notes, Loans and Financing Receivable [Line Items]
Loan-to-value ratio			15.00%
Accrual of interest			$ 14,800,000
Low auction estimate of collateral			$ 96,800,000

Receivables Schedule of Financi

Receivables Schedule of Financing Receivable Credit Quality Indicators (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Financing Receivable, Recorded Investment [Line Items]
Aggregate LTV ratio of Finance segment secured loans	50.00%
Loan To Value Ratio Above Fifty Percent
Financing Receivable, Recorded Investment [Line Items]
Finance segment secured loans	$ 168,116	$ 270,111
Low auction estimate of collateral	$ 269,063	$ 486,973
Aggregate LTV ratio of Finance segment secured loans	62.00%	55.00%
SFS
Financing Receivable, Recorded Investment [Line Items]
Finance segment secured loans	$ 590,609	$ 675,109
Low auction estimate of collateral	$ 1,369,235	$ 1,405,856
Aggregate LTV ratio of Finance segment secured loans	43.00%	48.00%

Receivables (Summary Of Other C

Receivables (Summary Of Other Credit Quality Information Regarding Finance Segment Secured Loans) (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total secured loans	$ 590,609,000	$ 675,109,000
Loans past due	62,570,000	90,508,000
Loans more than 90 days past due	56,087,000	158,000
Non-accrual loans	0	158,000
Impaired loans	0	0
Allowance for credit losses for impaired loans	0	0
Total allowance for credit losses - secured loans	2,778,000	1,270,000	$ 1,458,000
SFS
Segment Reporting Information [Line Items]
Impaired loans	0	0
Allowance for credit losses based on historical data	1,253,000	1,270,000
Total allowance for credit losses - secured loans	$ 1,253,000	$ 1,270,000	$ 1,458,000

Receivables (Activity Related T

Receivables (Activity Related To Allowance For Credit Losses) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Allowance for Loan and Lease Losses
Allowance for credit losses, beginning balance	$ 1,270	$ 1,458
Change in loan loss provision based on historical data	(17)	(188)
Change in loan loss provision for impaired loans	1,525
Allowance for credit losses, ending balance	2,778	1,270
SFS
Allowance for Loan and Lease Losses
Allowance for credit losses, beginning balance	1,270	1,458
Change in loan loss provision based on historical data	(17)	(188)
Change in loan loss provision for impaired loans	0
Allowance for credit losses, ending balance	1,253	1,270
Agency
Allowance for Loan and Lease Losses
Allowance for credit losses, beginning balance	0	0
Change in loan loss provision based on historical data	0	0
Change in loan loss provision for impaired loans	1,525
Allowance for credit losses, ending balance	$ 1,525	$ 0

Equity Method Investments (Deta

Equity Method Investments (Details) - USD ($) $ in Thousands	Feb. 18, 2015	May 23, 1990	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments			$ 6,542	$ 2,200	$ 30,725
Carrying value of the Matisse Inventory			33,900	39,000
Carrying value of investment			$ 46,905	43,143
AMA
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments		$ 153,000
Interest in partnership			50.00%
Carrying value of investment			$ 4,800	7,900
RM Auctions
Schedule of Equity Method Investments [Line Items]
Payments to acquire equity method investments	$ 30,700
Interest in partnership	25.00%
Carrying value of investment			$ 36,400	35,300
Other Equity Method Investment
Schedule of Equity Method Investments [Line Items]
Interest in partnership			50.00%
Carrying value of investment			$ 5,700
Reconciling items | Acquavella Modern Art
Schedule of Equity Method Investments [Line Items]
Equity earnings			1,700	1,300	2,800
Reconciling items | RM Auctions
Schedule of Equity Method Investments [Line Items]
Equity earnings			$ 1,200	$ 2,000	$ 2,500

Fixed Assets Fixed Assets (Deta

Fixed Assets Fixed Assets (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Property, Plant and Equipment [Line Items]
Land	$ 92,591	$ 92,591	$ 92,155
Buildings and building improvements	235,222	235,222	230,803
Leasehold improvements	84,504	84,504	72,969
Computer hardware and software	77,179	77,179	74,744
Furniture, fixtures and equipment	81,031	81,031	76,829
Construction in progress	9,492	9,492	3,621
Other	1,767	1,767	5,257
Sub-total	581,786	581,786	556,378
Less: Accumulated depreciation and amortization	(229,751)	(229,751)	(209,196)
Total Fixed Assets, net	352,035	352,035	347,182
Depreciation expense	$ 1,900
Depreciation and amortization		24,053	21,817	$ 19,481
Fixed Assets
Property, Plant and Equipment [Line Items]
Depreciation and amortization		$ 22,100	$ 19,900	$ 19,500

Goodwill and Intangible Asset73

Goodwill and Intangible Assets (Goodwill) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016
Changes in Goodwill
Beginning balance		$ 50,029	$ 13,621
Foreign currency exchange rate changes		518	(527)
Ending balance		50,547	50,029
AAP
Changes in Goodwill
Goodwill acquired		0	34,490
Orion Analytical
Changes in Goodwill
Goodwill acquired		0	2,445
Agency
Changes in Goodwill
Beginning balance		43,878	13,621
Foreign currency exchange rate changes		518	(527)
Ending balance		44,396	43,878
Agency | AAP
Changes in Goodwill
Goodwill acquired	$ 28,300	0	28,339
Agency | Orion Analytical
Changes in Goodwill
Goodwill acquired		0	2,445
All Other
Changes in Goodwill
Beginning balance		6,151	0
Foreign currency exchange rate changes		0	0
Ending balance		6,151	6,151
All Other | AAP
Changes in Goodwill
Goodwill acquired	$ 6,200	0	6,151
All Other | Orion Analytical
Changes in Goodwill
Goodwill acquired		$ 0	$ 0

Goodwill and Intangible Asset74

Goodwill and Intangible Assets (Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Indefinite-lived intangible assets	$ 324	$ 324
Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization	15,060	14,985
Accumulated amortization	(3,892)	(1,916)
Total amortizable intangible assets (net)	11,168	13,069
Total intangible assets (net)	$ 11,492	13,393
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Amortization Period	8 years
Intangible assets subject to amortization	$ 10,800	10,800
Non-compete agreements
Finite-Lived Intangible Assets [Line Items]
Amortization Period	6 years
Intangible assets subject to amortization	$ 3,060	3,060
Artworks database
Finite-Lived Intangible Assets [Line Items]
Amortization Period	10 years
Intangible assets subject to amortization	$ 1,200	$ 1,125

Goodwill and Intangible Asset75

Goodwill and Intangible Assets (Estimated Finite-Lived Intangible Asset Amortization by Fiscal Year Maturity) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization of intangible assets	$ 2,000,000	$ 1,900,000	$ 0
Finite-Lived Intangible Assets, Net, Amortization Expense
2,018	1,980,000
2,019	1,980,000
2,020	1,980,000
2,021	1,980,000
2,022	$ 1,470,000

Pension Arrangements (Retiremen

Pension Arrangements (Retirement Savings Plan Narrative) (Details) - Other pension plan - United States - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Retirement Savings Plan
Defined Benefit Plan Disclosure [Line Items]
Maximum annual contributions, percentage	50.00%
Employer matching, percentage	3.00%
Accrued discretionary employer contribution	$ 2.1	$ 1.2	$ 1.3
Accrued discretionary contribution, percentage		2.00%	2.00%
Contribution expense related to matching and discretionary contributions	$ 3.7	$ 2.5	$ 2.4
Retirement Savings Plan | Senior Vice President-level and above
Defined Benefit Plan Disclosure [Line Items]
Maximum annual contributions, percentage	25.00%
Retirement Savings Plan | Minimum | Senior Vice President-level and above
Defined Benefit Plan Disclosure [Line Items]
Pre-tax compensation, percentage	2.00%
Deferred Compensation Plan
Defined Benefit Plan Disclosure [Line Items]
Accrued discretionary employer contribution	$ 0.5	$ 0.3
Accrued discretionary contribution			$ 0.3
Accrued discretionary contribution, percentage	3.00%	2.00%	2.00%
Contribution expense related to matching and discretionary contributions	$ 0.9	$ 0.6	$ 0.8

Pension Arrangements (Deferred

Pension Arrangements (Deferred Compensation Plan Narrative) (Details) - Other pension plan - United States - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Death benefit recognized			$ 1.6
Deferred Compensation Plan
Defined Benefit Plan Disclosure [Line Items]
Accrued discretionary employer contribution	$ 0.5	$ 0.3
Accrued discretionary contribution, percentage	3.00%	2.00%	2.00%
Contribution expense related to matching and discretionary contributions	$ 0.9	$ 0.6	$ 0.8
DCP Liability	25.6	25.9
Gains (losses) in deemed participant investments	3.1	1.6	(0.5)
Net gains (losses) related to COLI and mutual fund investments	$ 2.6	$ 0.4	$ (2.7)

Pension Arrangements (Assets He

Pension Arrangements (Assets Held In Rabbi Trust) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Assets held in rabbi trust	$ 26,240	$ 26,713
Company-owned variable life insurance
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Assets held in rabbi trust	25,567	25,114
Mutual fund investments
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Assets held in rabbi trust	$ 673	$ 1,599

Pension Arrangements (U.K. Defi

Pension Arrangements (U.K. Defined Contribution Plan Narrative) (Details) - Other pension plan - U.K. plan - U.K. Defined Contribution Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Accrued discretionary employer contribution	$ 1.1	$ 1.1	$ 0.7
Accrued discretionary contribution, percentage	3.00%	2.00%	2.00%
Contribution expense related to matching and discretionary contributions	$ 4.5	$ 4.3	$ 3.1

Pension Arrangements (Change In

Pension Arrangements (Change In Benefit Obligation, Change In Fair Value Of Plan Assets, Funded Status And Amounts Recognized In Consolidated Balance Sheets) (Details) - Pension plan - U.K. Pension Plan - U.K. plan - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of benefit obligation
Projected benefit obligation at beginning of year		$ 327,619	$ 326,243
Service cost		0	1,086	$ 4,497
Interest cost		8,053	9,817	12,923
Contributions by plan participants		0	232
Actuarial (gain) loss		(781)	64,104
Benefits paid		(8,508)	(12,176)
Settlement payments		(11,880)	0
Foreign currency exchange rate changes		31,373	(61,687)
Benefit obligation at end of year	$ 327,619	345,876	327,619	326,243
Reconciliation of plan assets
Fair value of plan assets at beginning of year		406,195	393,102
Actual return on plan assets		28,827	73,806
Employer contributions	24,200	0	24,748
Contributions by plan participants		0	232
Benefits paid		(8,508)	(12,176)
Settlement payments		(11,880)	0
Foreign currency exchange rate changes		40,068	(73,517)
Fair value of plan assets at end of year	406,195	454,702	406,195	$ 393,102
Net pension asset	$ 78,576	$ 108,826	$ 78,576

Pension Arrangements (Benefit O

Pension Arrangements (Benefit Obligation, Plan Assets, and Funded Status Narrative) (Details) - Pension plan - U.K. plan - U.K. Pension Plan - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Amounts recorded within Other Long-Term Assets in Balance Sheets	$ 78,600	$ 108,800	$ 78,600
Settlement payments		(11,880)	0
Employer contributions	24,200	0	24,748
Accumulated benefit obligation	$ 327,600	$ 345,800	$ 327,600

Pension Arrangements (Component

Pension Arrangements (Components Of Net Pension Benefits Related To U.K. Pension Plan Assets) (Details) - Pension plan - U.K. plan - U.K. Pension Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 1,086	$ 4,497
Interest cost	8,053	9,817	12,923
Prior service cost	60	0	0
Expected return on plan assets	(14,159)	(17,798)	(20,174)
Amortization of actuarial loss	1,139	0	3,967
Amortization of prior service cost	(97)	0	364
Settlement loss	344	0	0
Net pension (benefit) cost	$ (4,660)	$ (6,895)	$ 1,577

Pension Arrangements (Other Com

Pension Arrangements (Other Comprehensive Income (Loss) Narrative) (Details) - Pension plan - U.K. plan - U.K. Pension Plan - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan Disclosure [Line Items]
Net unrecognized gains (losses) from defined benefit pension plan, net of tax of $xx, $6,445, and ($2,447)	$ 13.3	$ (6.5)	$ 29.4
Net loss included in accumulated other comprehensive loss	$ (1)	$ (14.2)
Threshold for recognizing net actuarial gains (losses)	10.00%
Expected remaining service lives	29 years 4 months 24 days
Market value of plan assets changes period	5 years
Amount to be amortized from accumulated other comprehensive income (loss) in next fiscal year	$ 0.3
Amount to be amortized from accumulated other comprehensive income (loss) in next fiscal year, pre-tax	$ 0.4

Pension Arrangements (Benefit84

Pension Arrangements (Benefit Obligation And Net Pension Benefit) (Details) - U.K. plan - U.K. Pension Plan	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Benefit Obligation
Weighted average discount rate	2.50%	2.70%
Net Pension (Benefit) Cost
Weighted average discount rate			3.50%
Weighted average discount rate - service cost		3.80%	3.50%
Weighted average discount rate - interest cost	2.40%	3.40%	3.50%
Weighted average rate of compensation increase		4.10%	4.10%
Weighted average expected long-term rate of return on plan assets	3.80%	5.20%	5.40%

Pension Arrangements (Plan Asse

Pension Arrangements (Plan Assets Narrative) (Details) - Pension plan - U.K. plan - U.K. Pension Plan - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Feb. 28, 2017
Defined Benefit Plan Disclosure [Line Items]
Employer contributions	$ 24,200	$ 0	$ 24,748
Growth assets
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets (as a percent)		23.00%		40.00%
Debt securities
Defined Benefit Plan Disclosure [Line Items]
Target allocation of plan assets (as a percent)		77.00%		60.00%

Pension Arrangements (Compone86

Pension Arrangements (Components Of U.K. Pension Plan Assets) (Details) - Pension plan - U.K. plan - U.K. Pension Plan - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	$ 454,702	$ 406,195	$ 393,102
Growth assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	$ 104,735	$ 217,730
Total debt securities, % of total	23.00%	53.60%
Total debt securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	$ 261,232	$ 170,945
Total debt securities, % of total	57.50%	42.10%
Corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	$ 41,804	$ 35,973
Total debt securities, % of total	9.20%	8.90%
Index-linked
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	$ 219,428	$ 134,972
Total debt securities, % of total	48.30%	33.20%
Real estate mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	$ 3,233	$ 2,667
Total debt securities, % of total	0.60%	0.60%
Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	$ 85,502	$ 14,853
Total debt securities, % of total	18.80%	3.70%

Pension Arrangements (Fair Valu

Pension Arrangements (Fair Value Measurement Information U.K. Pension Plan Assets) (Details) - Pension plan - U.K. plan - U.K. Pension Plan - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	$ 454,702	$ 406,195	$ 393,102
Quoted Prices in Active Markets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	451,469
Significant Other Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	3,233
Significant Unobservable Inputs (Level 3)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	0
Growth assets
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	104,735	217,730
Growth assets | Quoted Prices in Active Markets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	104,735
Growth assets | Significant Other Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	0
Growth assets | Significant Unobservable Inputs (Level 3)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	0
Total debt securities
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	261,232	170,945
Total debt securities | Quoted Prices in Active Markets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	261,232
Total debt securities | Significant Other Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	0
Total debt securities | Significant Unobservable Inputs (Level 3)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	0
Corporate
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	41,804	35,973
Corporate | Quoted Prices in Active Markets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	41,804
Corporate | Significant Other Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	0
Corporate | Significant Unobservable Inputs (Level 3)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	0
Index-linked
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	219,428	134,972
Index-linked | Quoted Prices in Active Markets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	219,428
Index-linked | Significant Other Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	0
Index-linked | Significant Unobservable Inputs (Level 3)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	0
Real estate mutual funds
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	3,233
Real estate mutual funds | Quoted Prices in Active Markets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	0
Real estate mutual funds | Significant Other Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	3,233
Real estate mutual funds | Significant Unobservable Inputs (Level 3)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	0
Cash and cash equivalents
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	85,502	$ 14,853
Cash and cash equivalents | Quoted Prices in Active Markets (Level 1)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	85,502
Cash and cash equivalents | Significant Other Observable Inputs (Level 2)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	0
Cash and cash equivalents | Significant Unobservable Inputs (Level 3)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Total fair value of plan assets	$ 0

Pension Arrangements (Estimated

Pension Arrangements (Estimated Future Benefit Payments) (Details) - Pension plan - U.K. Pension Plan - U.K. plan $ in Thousands	Dec. 31, 2017USD ($)
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
2,018	$ 9,323
2,019	8,798
2,020	9,729
2,021	12,013
2,022	11,362
2023 to 2027	$ 66,252

Debt (Revolving Credit Facility

Debt (Revolving Credit Facility) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Oct. 02, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt [Line Items]
Maximum borrowing capacity	$ 1,100,000,000		$ 1,335,000,000	$ 1,335,000,000
Borrowing base	$ 605,927,000		734,464,000	773,228,000
Incremental Facility extension period	365 days
Maximum net outstanding auction guarantees permitted	$ 600,000,000
Covenants for issuing dividends, minimum aggregate borrowing availability	100,000,000
Covenants for issuing dividends, minimum total liquidity amount	200,000,000
Other assets, noncurrent	5,400,000
New Credit Agreement
Debt [Line Items]
Maximum borrowing capacity	1,100,000,000
Line of credit, sub limit	320,000,000
Maximum increase in borrowing capacity	150,000,000
Aggregate fees paid	21,800,000
Incremental Credit Facility
Debt [Line Items]
Borrowing base	50,000,000
Agency Segment Credit Agreement
Debt [Line Items]
Maximum borrowing capacity	300,000,000		300,000,000	300,000,000
Borrowing base	148,299,000		165,443,000	225,642,000
Line of credit, sub limit	50,000,000
Finance Segment Credit Agreement
Debt [Line Items]
Decrease to borrowing capacity		$ 235,000,000
Maximum borrowing capacity	800,000,000		1,035,000,000	1,035,000,000
Borrowing base	457,628,000		$ 569,021,000	$ 547,586,000
Line of credit, sub limit	$ 270,000,000

Debt (Schedule of Line of Credi

Debt (Schedule of Line of Credit Facilities) (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 1,100,000,000	$ 1,335,000,000	$ 1,335,000,000
Borrowing base	605,927,000	734,464,000	773,228,000
Borrowings outstanding	196,500,000	565,000,000	541,500,000
Available borrowing capacity	409,427,000	169,464,000	231,728,000
Average borrowings outstanding	479,367,000	534,433,000	541,004,000
Borrowing Costs - interest	15,964,000	14,819,000	14,060,000
Borrowing Costs - fees	6,088,000	5,631,000	4,472,000
Interest expense	22,052,000	20,450,000	18,532,000
Agency Segment Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity	300,000,000	300,000,000	300,000,000
Borrowing base	148,299,000	165,443,000	225,642,000
Borrowings outstanding	0	0	0
Available borrowing capacity	148,299,000	165,443,000	225,642,000
Average borrowings outstanding	0	0	0
Borrowing Costs - interest	0	0	0
Borrowing Costs - fees	2,740,000	2,712,000	2,752,000
Interest expense	2,740,000	2,712,000	2,752,000
Finance Segment Credit Agreement
Line of Credit Facility [Line Items]
Maximum borrowing capacity	800,000,000	1,035,000,000	1,035,000,000
Borrowing base	457,628,000	569,021,000	547,586,000
Borrowings outstanding	196,500,000	565,000,000	541,500,000
Available borrowing capacity	261,128,000	4,021,000	6,086,000
Average borrowings outstanding	479,367,000	534,433,000	541,004,000
Borrowing Costs - interest	15,964,000	14,819,000	14,060,000
Borrowing Costs - fees	3,348,000	2,919,000	1,720,000
Interest expense	$ 19,312,000	$ 17,738,000	$ 15,780,000
Weighted average cost of borrowings (as a percent)	4.00%	3.30%	2.90%
Cost of finance revenues associated with reduction in borrowing capacity	$ 700,000

Debt (Summary Of Long-Term Debt

Debt (Summary Of Long-Term Debt) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt [Line Items]
Long-term debt, net	$ 653,003	$ 598,941
York Property Mortgage
Debt [Line Items]
Convertible notes, net of debt issuance costs	270,556	309,212
Less current portion	(11,930)	(6,629)
Unamortized debt issuance costs	4,545	5,555
Current unamortized debt issuance costs	1,010	1,010
Senior Notes | 2022 Senior Notes
Debt [Line Items]
Convertible notes, net of debt issuance costs	297,002	296,358
Less current portion	(297,002)	0
Unamortized debt issuance costs	2,998	3,642
Current unamortized debt issuance costs	2,998	0
Senior Notes | 2025 Senior Notes
Debt [Line Items]
Convertible notes, net of debt issuance costs	394,377	0
Unamortized debt issuance costs	$ 5,623	$ 0

Debt (York Property Mortgage) (

Debt (York Property Mortgage) (Details) - USD ($)	Jul. 03, 2017	Jul. 01, 2017	Nov. 21, 2016	Jul. 01, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 21, 2017	Jun. 20, 2017	Jun. 30, 2015	Feb. 06, 2009
Debt [Line Items]
Annual prepayments					$ 39,667,000	$ 7,302,000	$ 223,440,000
Equity					616,940,000	505,602,000
Interest rate swap
Debt [Line Items]
Derivative contract term			2 years
Minimum | York Property Mortgage
Debt [Line Items]
Debt instrument stated interest percentage										5.60%
Maximum | York Property Mortgage
Debt [Line Items]
Debt instrument stated interest percentage										10.60%
Mortgages
Debt [Line Items]
Annual prepayments	$ 32,000,000
Mortgages | New Mortgage Loan
Debt [Line Items]
Debt term				7 years
Principal amount				$ 325,000,000
Net cash proceeds from debt				$ 98,000,000
Derivative contract term				7 years
Maximum Loan-To-Value ratio under agreement (as a percent)				65.00%
Minimum debt yield under agreement (as a percent)				8.50%
Restricted cash and cash equivalents					3,100,000	$ 4,600,000
Minimum net worth under agreement					325,000,000
Mortgages | New Mortgage Loan | Interest rate swap
Debt [Line Items]
Derivative contract term				2 years
Mortgages | New Mortgage Loan | Collar
Debt [Line Items]
Derivative contract term				5 years
Mortgages | New Mortgage Loan | LIBOR
Debt [Line Items]
Basis spread on variable rate (as a percent)				2.25%
Mortgages | York Property Mortgage
Debt [Line Items]
Debt term		7 years
Amortization period				25 years
Minimum net worth required for compliance								$ 325,000,000	$ 425,000,000
Mortgages | York Property Mortgage | Interest rate swap
Debt [Line Items]
Derivative contract term				2 years
Mortgages | Maximum
Debt [Line Items]
Annual prepayments	25,000,000
Assumption Of Existing Mortgage
Debt [Line Items]
Components of purchase price of land and buildings											$ 235,000,000
Parent Company
Debt [Line Items]
Equity					$ 616,900,000
Cash | Mortgages
Debt [Line Items]
Annual prepayments	25,000,000
Restricted Cash | Mortgages
Debt [Line Items]
Annual prepayments	$ 7,000,000
Standard & Poor's, B Rating | Mortgages | York Property Mortgage
Debt [Line Items]
Required debt service					12 months
Standard & Poor's, B Plus Rating | Mortgages | York Property Mortgage
Debt [Line Items]
Required debt service					6 months

Debt (Senior Unsecured Debt) (D

Debt (Senior Unsecured Debt) (Details) - USD ($)	Jan. 11, 2018	Dec. 12, 2017	Sep. 28, 2012	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jun. 15, 2013	Nov. 23, 2012	Sep. 27, 2012
Debt [Line Items]
Accrued interest				$ 51,807,000	$ 44,502,000	$ 53,461,000
Senior Notes
Debt [Line Items]
Unsecured debt retired								$ 80,000,000
Convertible Notes
Debt [Line Items]
Unsecured debt retired							$ 182,000,000
2022 Senior Notes | Senior Notes
Debt [Line Items]
Principal amount									$ 300,000,000
Debt instrument stated interest percentage									5.25%
Net proceeds from issuance of long term debt			$ 294,600,000
Fair value				307,500,000
2022 Senior Notes | Senior Notes | Subsequent Event
Debt [Line Items]
Principal amount	$ 300,000,000
Amount redeemed	312,300,000
Accrued interest	4,400,000
Payment for debt extinguishment	7,900,000
Write off of debt issuance cost	3,000,000
Loss on extinguishment	$ 10,900,000
2025 Senior Notes | Senior Notes
Debt [Line Items]
Principal amount		$ 400,000,000
Debt instrument stated interest percentage		4.875%
Net proceeds from issuance of long term debt		$ 395,500,000
Fair value				$ 392,500,000
Amount deposited to trustee		$ 312,300,000
2025 Senior Notes | Senior Notes | Prior to December 15, 2020
Debt [Line Items]
Percentage of principal amount redeemed		100.00%
2025 Senior Notes | Senior Notes | After December 15, 2020
Debt [Line Items]
Percentage of principal amount redeemed		40.00%
Redemption percentage		104.875%
2025 Senior Notes | Senior Notes | Change of Control
Debt [Line Items]
Percentage of principal amount redeemed		101.00%

Debt (Aggregate Future Principa

Debt (Aggregate Future Principal And Interest Payments) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Jul. 01, 2015
Debt Instruments [Abstract]
2,018	$ 356,264
2,019	42,530
2,020	238,963
2,021	42,931
2,022	$ 247,131
Collar | Mortgages | New Mortgage Loan | Minimum
Debt [Line Items]
Effective interest rate (as a percent)		4.167%

Debt (Interest Paid) (Details)

Debt (Interest Paid) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Debt Conversion [Line Items]
Interest paid	$ 51,807	$ 44,502	$ 53,461
Debt issuance and other borrowing costs	(5,729)	(320)	(9,642)
Agency Segment Credit Agreement
Debt Conversion [Line Items]
Interest paid	33,745	27,793	35,948
Finance Segment Credit Agreement
Debt Conversion [Line Items]
Interest paid	$ 18,062	$ 16,709	$ 17,513

Derivative Financial Instrume96

Derivative Financial Instruments (Schedule of Fair Value Information Related to Derivative Financial Instruments) (Details) - Designated as Hedging Instruments - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivatives, Fair Value [Line Items]
Assets	$ 339	$ 30,340
Liabilities	5,923	6,115
Cash Flow Hedges
Derivatives, Fair Value [Line Items]
Assets	339	82
Liabilities	2,167	6,115
Cash Flow Hedges | Interest rate swap | Other Current Assets
Derivatives, Fair Value [Line Items]
Assets	339	82
Cash Flow Hedges | Interest rate swap | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Liabilities		163
Cash Flow Hedges | Interest rate collar | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Liabilities	666
Cash Flow Hedges | Interest rate collar | Other Long-Term Liabilities
Derivatives, Fair Value [Line Items]
Liabilities	1,501	5,952
Net Investment Hedges | Foreign exchange contracts
Derivatives, Fair Value [Line Items]
Liabilities		0
Net Investment Hedges | Foreign exchange contracts | Other Current Assets
Derivatives, Fair Value [Line Items]
Assets		$ 30,258
Net Investment Hedges | Foreign exchange contracts | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Liabilities	$ 3,756

Derivative Financial Instrume97

Derivative Financial Instruments (Narrative) (Details) - USD ($) $ in Thousands	Jul. 03, 2017	Jul. 01, 2017	Nov. 21, 2016	Jul. 01, 2015	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 31, 2021
Derivative [Line Items]
Realized net gain							$ 29,110	$ (3,308)	$ 0
Initial period under interest rate protection agreements							2 years
Reduction to notional amount of derivative					$ 57,000
Annual prepayments							$ 39,667	7,302	223,440
SFS Credit Facility borrowings			$ 63,000
Mortgages
Derivative [Line Items]
Annual prepayments	$ 32,000
Mortgages | Maximum
Derivative [Line Items]
Annual prepayments	$ 25,000
Mortgages | Scenario, Forecast | Minimum
Derivative [Line Items]
Annual prepayments										$ 6,250
Mortgages | York Property Mortgage
Derivative [Line Items]
Term of mortgage loan		7 years
Interest rate swap
Derivative [Line Items]
Term of derivative contract			2 years
Interest rate swap | Mortgages | York Property Mortgage
Derivative [Line Items]
Term of derivative contract				2 years
Fixed annual rate				0.877%
Annual interest rate taking into account the interest rate protection agreements					3.127%	3.127%
Interest rate swap | Credit Facility borrowings
Derivative [Line Items]
Notional value of derivative							63,000
Interest rate collar
Derivative [Line Items]
Notional value of derivative							$ 275,100
Interest rate collar | Mortgages | York Property Mortgage
Derivative [Line Items]
Term of derivative contract		5 years
Interest rate collar | Mortgages | York Property Mortgage | Minimum
Derivative [Line Items]
Fixed annual rate		1.917%
Annual interest rate taking into account the interest rate protection agreements							4.167%
Interest rate collar | Mortgages | York Property Mortgage | Maximum
Derivative [Line Items]
Fixed annual rate		3.75%
Annual interest rate taking into account the interest rate protection agreements							6.00%
Foreign exchange contracts
Derivative [Line Items]
Notional value of derivative							$ 134,400
Forward exchange contracts
Derivative [Line Items]
Current derivative liability							800	3,600
Designated as Hedging Instruments
Derivative [Line Items]
Reduction in notional amount of derivative reclassified from Accumulated Other Comprehensive Loss into Net Income							(622)	0	0
Net investment hedges | Designated as Hedging Instruments | Foreign exchange contracts
Derivative [Line Items]
Aggregate notional value							213,800
Realized net gain							29,100
Notional value of derivative							49,700
Cash flow hedges | Designated as Hedging Instruments
Derivative [Line Items]
Reduction in notional amount of derivative reclassified from Accumulated Other Comprehensive Loss into Net Income							$ (622)	$ 0	$ 0
Cash flow hedges | Non-operating income | Designated as Hedging Instruments | Interest rate collar
Derivative [Line Items]
Reduction in notional amount of derivative reclassified from Accumulated Other Comprehensive Loss into Net Income						$ 600

Derivative Financial Instrume98

Derivative Financial Instruments (Summary of the Effect of the Derivative Financial Instruments) (Details) - Designated as Hedging Instruments - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Derivative Instruments
Gain (Loss) Recognized in Other Comprehensive Income (Loss) - Effective Portion		$ (1,639,000)	$ 16,447,000	$ (4,994,000)
Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Effective Portion		593,000	813,000	688,000
Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Ineffective Portion		622,000	0	0
Cash Flow Hedges
Derivative Instruments
Gain (Loss) Recognized in Other Comprehensive Income (Loss) - Effective Portion		1,420,000	(171,000)	(4,994,000)
Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Effective Portion		593,000	813,000	688,000
Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Ineffective Portion		622,000	0	0
Cash Flow Hedges | Interest rate swap
Derivative Instruments
Gain (Loss) Recognized in Other Comprehensive Income (Loss) - Effective Portion		201,000	(704,000)	(802,000)
Cash Flow Hedges | Interest rate swap | Interest Expense
Derivative Instruments
Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Effective Portion		16,000	813,000	688,000
Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Ineffective Portion		0	0	0
Cash Flow Hedges | Interest rate collar
Derivative Instruments
Gain (Loss) Recognized in Other Comprehensive Income (Loss) - Effective Portion		1,219,000	533,000	(4,192,000)
Cash Flow Hedges | Interest rate collar | Interest Expense
Derivative Instruments
Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Effective Portion		577,000	0	0
Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Ineffective Portion		0	0	0
Cash Flow Hedges | Interest rate collar | Non-operating income
Derivative Instruments
Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Ineffective Portion	$ (600,000)
Cash Flow Hedges | Interest rate collar
Derivative Instruments
Gain (Loss) Recognized in Other Comprehensive Income (Loss) - Effective Portion		0	0	0
Cash Flow Hedges | Interest rate collar | Non-operating income
Derivative Instruments
Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Effective Portion		0	0	0
Amount Reclassified from Accumulated Other Comprehensive Loss into Net Income - Ineffective Portion		622,000	0	0
Net Investment Hedges | Foreign exchange contracts
Derivative Instruments
Gain (Loss) Recognized in Other Comprehensive Income (Loss) - Effective Portion		$ (3,059,000)	$ 16,618,000	$ 0

Sale of Pink Diamond (Details)

Sale of Pink Diamond (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended								12 Months Ended
	Apr. 30, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Product Information [Line Items]
Undivided legal and beneficial ownership interest sold (as a percent)								50.00%
Cash received for undivided legal and beneficial interest								$ 34,200
Inventory sales		$ 6,167	$ 81,501	$ 19,937	$ 71,377	$ 26,429	$ 24,359	$ 5,281	$ 6,794	$ 178,982	$ 62,863	$ 108,699
Inventory		74,483				$ 159,043				74,483	$ 159,043
Pink Diamond
Product Information [Line Items]
Inventory sales	$ 71,200
Inventory		$ 68,400								68,400
Gain on sale of Pink Diamond										400
Cost of Inventory Sales										$ 70,800

Supplemental Consolidated Ba100

Supplemental Consolidated Balance Sheet Information (Schedule of Prepaid Expenses and Other Current Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Prepaid expenses	$ 25,418	$ 20,436
Derivative financial instruments	339	30,340
Insurance recoveries	0	19,884
Other	6,253	5,947
Total Prepaid and Other Current Assets	$ 32,010	$ 76,607

Supplemental Consolidated Ba101

Supplemental Consolidated Balance Sheet Information (Narrative) (Details) - Designated as Hedging Instruments - Foreign exchange contracts - Net investment hedges - USD ($) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Dec. 31, 2017
Derivative Instruments
Aggregate notional value		$ 213.8
Realized net gain	$ 29.1

Supplemental Consolidated Ba102

Supplemental Consolidated Balance Sheet Information (Schedule of Other Long-Term Assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Defined benefit pension plan asset (see Note 8)	$ 108,826	$ 78,576
Equity method investments (see Note 5)	46,905	43,143
Trust assets related to deferred compensation liability (see Note 8)	26,240	26,713
Restricted cash	17,916	1,064
Insurance recoveries	12,242	0
Other	15,479	15,928
Total Other Long-Term Assets	227,608	$ 165,424
Funds held in escrow	$ 15,300

Supplemental Consolidated Ba103

Supplemental Consolidated Balance Sheet Information (Schedule of Other Long-Term Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Deferred compensation liability (see Note 8)	$ 25,614	$ 25,914
Acquisition earn-out consideration (see Note 3)	17,500	26,250
Interest rate collar liability (see Note 10)	1,501	5,952
Other	6,809	6,964
Total Other Long-Term Liabilities	$ 51,424	$ 65,080

Supplemental Consolidated Ca104

Supplemental Consolidated Cash Flow Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Decrease (increase) in:
Prepaid expenses and other current assets	$ 17,160	$ (14,510)	$ (6,562)
Other long-term assets	(10,349)	(10,006)	13,641
Income tax receivables and deferred income tax assets	(33,532)	2,395	22,144
(Decrease) increase in:
Accrued income taxes and deferred income tax liabilities	35,421	14,879	(27,325)
Accounts payable and accrued liabilities and other liabilities	(14,189)	17,297	(29,530)
Total changes in other operating assets and liabilities	$ (5,489)	$ 10,055	$ (27,632)

Shareholders' Equity and Div105

Shareholders' Equity and Dividends (Details) - USD ($)	Feb. 28, 2018	Aug. 15, 2017	Oct. 03, 2016	Jan. 21, 2016	Aug. 13, 2015	Aug. 06, 2015	Mar. 17, 2014	Jan. 29, 2014	Mar. 31, 2017	Mar. 31, 2016	Nov. 30, 2015	Aug. 31, 2015	Mar. 31, 2015	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2017
Dividends Payable [Line Items]
Common stock, par value (usd per share)															$ 0.01	$ 0.01		$ 0.01	$ 0.01
Common stock, shares outstanding															52,461,996	52,971,232		52,461,996	52,461,996
Preferred stock, shares authorized (in shares)															50,000,000			50,000,000	50,000,000
Preferred stock, shares outstanding (in shares)															0	0		0	0
Increase in authorized amount		$ 100,000,000		$ 200,000,000		$ 125,000,000								$ 75,000,000
Stock repurchase program, authorized amount		$ 100,030,000		$ 325,000,000		$ 250,000,000
Treasury stock acquired (in shares)			2,050,000		2,667,378						1,038,280	3,705,658			961,000	13,144,000	3,706,000	17,811,000
Initial purchase price					$ 125,000,000
Aggregate purchase price					$ 100,000,000										$ 44,495,000	$ 359,885,000	$ 125,000,000	$ 529,380,000
Cost per share of stock acquired (usd per share)			$ 36		$ 37.49							$ 33.73			$ 46.32	$ 27.38	$ 33.73	$ 29.72
Stock repurchased during period, value			$ 73,800,000
Ownership percentage in Sotheby's outstanding Common Stock prior to sale			8.50%
Dividends declared (usd per share)				$ 0.10													$ 0.40
Cash dividend equivalents paid on share-based payments									$ 2,000,000	$ 1,400,000			$ 2,000,000				$ 279,000		$ 9,200,000
Subsequent Event
Dividends Payable [Line Items]
Increase in authorized amount	$ 100,000,000
Stock repurchase program, authorized amount	$ 195,700,000
Special Dividend
Dividends Payable [Line Items]
Dividends declared (usd per share)								$ 4.34
Dividends, common stock								$ 300,000,000
Share-based compensation based on special dividends							$ 10,000,000

Shareholders' Equity and Div106

Shareholders' Equity and Dividends (Common Stock Share Repurchase Program) (Details) - USD ($) $ / shares in Units, $ in Thousands	Oct. 03, 2016	Aug. 13, 2015	Nov. 30, 2015	Aug. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Shareholders' Equity and Dividends [Abstract]
Shares repurchased (in shares)	2,050,000	2,667,378	1,038,280	3,705,658	961,000	13,144,000	3,706,000	17,811,000
Aggregate purchase price		$ 100,000			$ 44,495	$ 359,885	$ 125,000	$ 529,380
Average price per share (usd per share)	$ 36	$ 37.49		$ 33.73	$ 46.32	$ 27.38	$ 33.73	$ 29.72

Shareholders' Equity and Div107

Shareholders' Equity and Dividends (Schedule of Quarterly Dividends Declared and Paid) (Details) - USD ($) $ / shares in Units, $ in Thousands	Jan. 21, 2016	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Dividends Payable [Line Items]
Dividends declared (usd per share)	$ 0.10															$ 0.40
Quarterly Dividend
Dividends Payable [Line Items]
Dividends declared (usd per share)		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0.1	$ 0.10	$ 0.10	$ 0.10	$ 0	$ 0	$ 0.4
Dividends		$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 6,563	$ 6,667	$ 6,933	$ 6,944	$ 0	$ 0	$ 27,107

Accumulated Other Comprehens108

Accumulated Other Comprehensive Loss (Changes in Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Changes in Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period	$ 505,418	$ 806,427	$ 877,697
Reclassifications from other comprehensive (loss) income	2,365	813	4,047
Total other comprehensive income (loss)	27,892	(24,154)	10,562
Balance at end of period	616,755	505,418	806,427
Accumulated Other Comprehensive Loss
Changes in Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period	(90,358)	(66,204)	(76,766)
Total other comprehensive income (loss)	27,892	(24,154)	10,562
Balance at end of period	(62,466)	(90,358)	(66,204)
Currency Translation Adjustments
Changes in Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period	(89,478)	(52,279)	(33,223)
Other comprehensive (loss) income before reclassifications, net of tax	14,973	(37,199)	(18,951)
Reclassifications from other comprehensive (loss) income	0	0	(105)
Total other comprehensive income (loss)	14,973	(37,199)	(19,056)
Balance at end of period	(74,505)	(89,478)	(52,279)
Other comprehensive income (loss) before reclassifications, tax	1,760	(13,113)	(6,345)
Derivative Financial Instruments | Cash Flow Hedges
Changes in Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period	(3,664)	(4,306)	0
Other comprehensive (loss) income before reclassifications, net of tax	1,420	(171)	(4,994)
Reclassifications from other comprehensive (loss) income	1,215	813	688
Total other comprehensive income (loss)	2,635	642	(4,306)
Balance at end of period	(1,029)	(3,664)	(4,306)
Other comprehensive income (loss) before reclassifications, tax	888	(106)	(3,126)
Reclassification from AOCI, current period, tax	753	502	430
Derivative Financial Instruments | Net Investment Hedges
Changes in Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period	16,618	0	0
Other comprehensive (loss) income before reclassifications, net of tax	(3,059)	16,618	0
Total other comprehensive income (loss)	(3,059)	16,618	0
Balance at end of period	13,559	16,618	0
Other comprehensive income (loss) before reclassifications, tax	(1,885)	10,354	0
Defined Benefit Pension Items
Changes in Accumulated Other Comprehensive Income (Loss)
Balance at beginning of period	(13,834)	(9,619)	(43,543)
Other comprehensive (loss) income before reclassifications, net of tax	12,193	(4,215)	30,460
Reclassifications from other comprehensive (loss) income	1,150	0	3,464
Total other comprehensive income (loss)	13,343	(4,215)	33,924
Balance at end of period	(491)	(13,834)	(9,619)
Currency translation adjustments
Changes in Accumulated Other Comprehensive Income (Loss)
Other comprehensive (loss) income before reclassifications, net of tax	(1,084)	2,300	1,097
Net actuarial (loss) gain
Changes in Accumulated Other Comprehensive Income (Loss)
Other comprehensive (loss) income before reclassifications, net of tax	13,277	(6,515)	29,363
Other comprehensive income (loss) before reclassifications, tax	2,719	(1,427)	6,445
Prior service cost amortization
Changes in Accumulated Other Comprehensive Income (Loss)
Reclassifications from other comprehensive (loss) income	(80)	0	291
Reclassification from AOCI, current period, tax	(17)	0	73
Actuarial loss amortization
Changes in Accumulated Other Comprehensive Income (Loss)
Reclassifications from other comprehensive (loss) income	945	0	3,173
Reclassification from AOCI, current period, tax	194	0	794
Settlement cost
Changes in Accumulated Other Comprehensive Income (Loss)
Reclassifications from other comprehensive (loss) income	285	0	0
Reclassification from AOCI, current period, tax	$ 59	$ 0	$ 0

Accumulated Other Comprehens109

Accumulated Other Comprehensive Loss (Reclassifications) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustments, net of tax	$ 2,365	$ 813	$ 4,047
Currency Translation Adjustments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustments, net of tax	0	0	(105)
Defined Benefit Pension Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustments, net of tax	1,150	0	3,464
Prior service cost amortization
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax effect	17	0	(73)
Reclassification adjustments, net of tax	(80)	0	291
Settlement loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax effect	(59)	0	0
Reclassification adjustments, net of tax	285	0	0
Actuarial loss amortization
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax effect	(194)	0	(794)
Reclassification adjustments, net of tax	945	0	3,173
Reclassification out of Accumulated Other Comprehensive Loss | Currency Translation Adjustments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification before tax	0	0	(105)
Tax effect	0	0	0
Reclassification adjustments, net of tax	0	0	(105)
Reclassification out of Accumulated Other Comprehensive Loss | Derivative Financial Instruments
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification before tax	1,968	1,315	1,118
Tax effect	(753)	(502)	(430)
Reclassification adjustments, net of tax	1,215	813	688
Reclassification out of Accumulated Other Comprehensive Loss | Defined Benefit Pension Items
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification before tax	1,386	0	4,331
Tax effect	(236)	0	(867)
Reclassification adjustments, net of tax	1,150	0	3,464
Reclassification out of Accumulated Other Comprehensive Loss | Prior service cost amortization
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification before tax	(97)	0	364
Reclassification out of Accumulated Other Comprehensive Loss | Settlement loss
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification before tax	344	0	0
Reclassification out of Accumulated Other Comprehensive Loss | Actuarial loss amortization
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification before tax	$ 1,139	$ 0	$ 3,967

Income Taxes (Summary Of Signif

Income Taxes (Summary Of Significant Components Of Income Tax Expense) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income before taxes:
Domestic	$ 3,636	$ (38,567)	$ 11,414
Foreign	138,050	135,301	157,885
Income before taxes	141,686	96,734	169,299
Income tax expense—current:
Domestic	24,427	18,443	10,455
State and local	1,492	1,766	5,958
Foreign	27,481	29,904	33,043
Sub-total	53,400	50,113	49,456
Income tax (benefit) expense—deferred:
Domestic	(34,501)	(19,114)	69,835
State and local	1,285	(1,034)	6,378
Foreign	5,231	(4,008)	5,476
Sub-total	(27,985)	(24,156)	81,689
Income tax expense, Total	$ 25,415	$ 25,957	$ 131,145

Income Taxes (Summary Of Compon

Income Taxes (Summary Of Components Of Deferred Tax Assets And Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Asset provisions and liabilities	$ 4,832	$ 11,512
Inventory writedowns	3,408	10,874
Tax loss and credit carryforwards	3,908	3,708
Difference between book and tax basis of depreciable and amortizable assets	20,218	30,855
Share-based payments and deferred compensation	15,130	26,267
Sub-total	47,496	83,216
Valuation allowance	(3,194)	(2,819)
Total deferred tax assets	44,302	80,397
Deferred tax liabilities:
Difference between book and tax basis of other assets and liabilities	859	1,612
Pension obligations	16,280	9,689
Basis differences in equity method investments	1,269	3,423
Undistributed earnings of foreign subsidiaries	2,571	68,201
Bond redemption costs	2,812	0
Total deferred tax liabilities	23,791	82,925
Total net deferred tax assets (liabilities)	$ 20,511
Total net deferred tax assets (liabilities)		$ (2,528)

Income Taxes (Narrative) (Detai

Income Taxes (Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Contingency [Line Items]
Deferred tax assets, foreign and state loss and tax credit carryforwards	$ 3,900		$ 3,900
Valuation allowance	3,194		$ 3,194	$ 2,819
Effective income tax rate			17.90%	26.80%	77.50%
Provisional income tax expense	1,200
Provisional non-cash income tax expense, deferred tax assets	19,800
Provisional income tax expense, unremitted and untaxed earnings of our foreign subsidiaries	40,400
Non-cash income tax benefit, deferred tax liabilities	59,000		$ 59,000
Provisional liability, current	34,600		34,600
Provisional liability, noncurrent	$ 32,000		32,000
Foreign earnings that have not yet repatriated			460,000
WithholdingTaxRepatriation			3,500
Net income tax payments			$ 52,300	$ 32,400	$ 53,900
Scenario, Forecast
Income Tax Contingency [Line Items]
Foreign earnings repatriated		$ 325,000

Income Taxes (Summary Of Effect

Income Taxes (Summary Of Effective Income Tax Rate) (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income Tax Expense (Benefit), Continuing Operations, Adjustment of Deferred Tax (Asset) Liability	$ 19.8
Statutory federal income tax rate		35.00%	35.00%	35.00%
State and local taxes, net of federal tax benefit		0.80%	0.50%	2.30%
Foreign taxes at rates different from U.S. rates		(13.50%)	(25.00%)	(14.90%)
U.S. taxes on foreign earnings		1.20%	9.90%	50.50%
Valuation allowance		0.00%	0.50%	0.30%
Effect of enacted tax legislation		0.80%	(0.10%)	2.50%
Changes in tax reserves		(4.50%)	1.60%	0.00%
Other		(1.90%)	4.40%	1.80%
Effective income tax rate		17.90%	26.80%	77.50%

Uncertain Tax Positions (Narrat

Uncertain Tax Positions (Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Uncertainties [Abstract]
Unrecognized tax benefits	$ 13,174	$ 19,478	$ 22,042	$ 22,798
Unrecognized tax benefits that would impact effective tax rate	4,100	9,300
Unrecognized tax benefits, income tax and interest penalties (benefits)	(900)	300	(40)
Unrecognized tax benefits, income tax penalties and interest accrued	1,200	$ 2,100	$ 1,800
Decrease in unrecognized tax benefits within 12 months	$ 1,800

Uncertain Tax Positions (Reconc

Uncertain Tax Positions (Reconciliation Of Beginning And Ending Balances Of Liability For Unrecognized Tax Benefits, Excluding Interest And Penalties) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance at January 1	$ 19,478	$ 22,042	$ 22,798
Increases in unrecognized tax benefits related to the current year	2,512	1,700	2,917
Increases in unrecognized tax benefits related to prior years	2,430	29	2,276
Decreases in unrecognized tax benefits related to prior years	(793)	0	(1,973)
Decreases in unrecognized tax benefits related to settlements	(2,075)	0	(437)
Decreases in unrecognized tax benefits due to the lapse of the applicable statute of limitations	(8,378)	(4,293)	(3,539)
Balance at December 31	$ 13,174	$ 19,478	$ 22,042

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Millions	Feb. 28, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Commitment for salaries and other cash compensation under employment arrangement		$ 16.3
Subsequent Event
Loss Contingencies [Line Items]
Guarantee of collection	$ 26

Auction Guarantees (Details)

Auction Guarantees (Details) - USD ($)	Feb. 26, 2018	Dec. 31, 2017	Dec. 31, 2016
Guarantor Obligations [Line Items]
Maximum net outstanding auction guarantees permitted		$ 600,000,000
Outstanding guarantee maximum exposure		28,000,000
Irrevocable bids		11,800,000
Estimated fair value of obligation to perform under auction guarantees		900,000	$ 600,000
Subsequent Event
Guarantor Obligations [Line Items]
Outstanding guarantee maximum exposure	$ 316,200,000
Irrevocable bids	277,600,000
Auction guarantee advances outstanding	$ 500,000
Agency
Guarantor Obligations [Line Items]
Auction guarantee advances outstanding		$ 0	$ 1,000,000

Lease Commitments (Narrative) (

Lease Commitments (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Leases, Operating [Abstract]
Rental expense under operating leases	$ 18.7	$ 18.4	$ 17.5
Future minimum sublease rental receipts	$ 13.2

Lease Commitments (Schedule Of

Lease Commitments (Schedule Of Future Minimum Rental Payments For Operating Leases) (Details) $ in Thousands	Dec. 31, 2017USD ($)
Leases [Abstract]
2,018	$ 19,196
2,019	17,086
2,020	15,566
2,021	11,742
2,022	9,425
Thereafter	29,672
Total future minimum lease payments	$ 102,687

Share-Based Payments (Compensat

Share-Based Payments (Compensation Expense Related To Share-Based Payments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation Expense Related to Share-Based Payments
Total share-based payment expense (pre-tax)	$ 23,479	$ 15,216	$ 33,700
Total share-based payment expense (after-tax)	15,555	10,810	22,992
Salaries and related costs
Compensation Expense Related to Share-Based Payments
Total share-based payment expense (pre-tax)	23,479	15,935	28,632
CEO separation and transition costs
Compensation Expense Related to Share-Based Payments
Total share-based payment expense (pre-tax)	0	0	2,000
Voluntary separation incentive programs | Voluntary separation incentive programs
Compensation Expense Related to Share-Based Payments
Total share-based payment expense (pre-tax)	$ 0	$ (719)	$ 3,068

Share-Based Payments (Share-Bas

Share-Based Payments (Share-Based Payment Awards Narrative) (Details) - USD ($) $ in Thousands	2 Months Ended	3 Months Ended	12 Months Ended
	Feb. 28, 2018	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Excess tax benefits related to share-based payment arrangements			$ 2,700		$ 1,064
Tax shortfall related to share-based payment arrangements				$ (1,342)
Unrecognized compensation expense related to the unvested portion of share-based payments			$ 22,400
Compensation expense is expected to be amortized over a weighted-average period			1 year 10 months 24 days
Granted (shares)			788,000
Share-based payment expense (credit)			$ 23,479	15,216	33,700
Restricted Stock Unit Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of stock granted during period			$ 31,600
New CEO 2015 Agreement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of stock granted during period		$ 16,500
2017 Share-Based Payment Awards | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of stock granted during period	$ 29,400
Performance Shares | Single vesting opportunity after three years of service
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Fair value of stock granted during period			$ 14,600
Granted (shares)			369,897
Maximum vesting percentage for incremental PSU's			100.00%
Performance Shares | Single vesting opportunity after three years of service | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Fair value of stock granted during period	$ 13,100
Granted (shares)	283,019
Maximum vesting percentage for incremental PSU's	100.00%
Performance Shares | New CEO 2015 Agreement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period		5 years
Fair value of stock granted during period		$ 8,000
Granted (shares)		94,140
Performance Shares | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Performance Shares | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Performance Shares | Maximum | Single vesting opportunity after three years of service
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (shares)			739,794
Maximum vesting percentage for incremental PSU's			200.00%
Performance Shares | Maximum | Single vesting opportunity after three years of service | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (shares)	566,038
Maximum vesting percentage for incremental PSU's	200.00%
Performance Shares | Maximum | New CEO 2015 Agreement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Granted (shares)		329,490
Maximum vesting percentage for incremental PSU's		350.00%
Restricted Stock | New CEO 2015 Agreement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of stock granted during period		$ 6,500
Granted (shares)		158,638
Restricted Stock Units (RSUs) | Restricted Stock Unit Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Restricted Stock Units (RSUs) | Restricted Stock Unit Plan | Annual vesting over three years
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			3 years
Fair value of stock granted during period			$ 17,000
Granted (shares)			418,447
Restricted Stock Units (RSUs) | New CEO 2015 Agreement
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Fair value of stock granted during period		$ 2,000
Granted (shares)		47,070
Restricted Stock Units (RSUs) | 2017 Share-Based Payment Awards | Annual vesting over three years | Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	3 years
Fair value of stock granted during period	$ 16,300
Granted (shares)	346,508
Restricted Stock Restricted Stock Unit And Performance Share Unit
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares available for future awards (shares)			2,400,000
Fair value of share vested			$ 39,700	$ 15,200	$ 22,900

Share-Based Payments (Changes I

Share-Based Payments (Changes In Number Of Outstanding Restricted Stock, RSU's And PSU's) (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2017$ / sharesshares
RSU's, PSU's, and Restricted Stock Shares
Outstanding beginning balance, Shares | shares	2,235
Granted, Shares | shares	788
Vested, Shares | shares	(838)
Canceled, Shares | shares	(263)
Outstanding ending balance, Shares | shares	1,922
Weighted Average Grant Date Fair Value
Outstanding beginning balance (usd per share) | $ / shares	$ 36.40
Granted (usd per share) | $ / shares	40.12
Vested (usd per share) | $ / shares	39.20
Canceled (usd per share) | $ / shares	37.27
Outstanding ending balance (usd per share) | $ / shares	$ 36.59

Share-Based Payments (Stock Opt

Share-Based Payments (Stock Options Narrative) (Details) - USD ($) $ / shares in Units, $ in Millions	1 Months Ended	3 Months Ended	12 Months Ended
	Jan. 31, 2018	Dec. 31, 2017	Dec. 31, 2017
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, expiration term			10 years
Remaining shares (in shares)			50,000
Exercisable (in shares)		0	0
Options outstanding, weighted average exercise price (usd per share)			$ 22.11
Options outstanding, aggregate intrinsic value			$ 1.4
Tax benefit from exercise of stock options		$ 0.2
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Proceeds from exercise of employee stock options	$ 1.1
Equity Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period			4 years
Options outstanding (shares)		0	0
Common stock were available for the issuance (in shares)		104,100	104,100

Share-Based Payments (Directors

Share-Based Payments (Directors Stock Plan Narrative) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment expense (credit)	$ 23,479	$ 15,216	$ 33,700
Outstanding (in shares)	1,922,000	2,235,000
Director's Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based payment expense (credit)	$ 1,000	$ 900	$ 1,000
Outstanding (in shares)	168,799
Shares available for future awards (shares)	114,869

Voluntary Separation Incenti125

Voluntary Separation Incentive Programs, net (Details) - Voluntary separation incentive programs - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring charges (credit), net	$ 36,900	$ (162)	$ (610)	$ 36,938
Employee severance
Restructuring Cost and Reserve [Line Items]
Restructuring charges (credit), net	33,800
Accelerated equity compensation expense
Restructuring Cost and Reserve [Line Items]
Restructuring charges (credit), net	$ 3,100

CEO Separation and Transitio126

CEO Separation and Transition Costs (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended	12 Months Ended
	Sep. 30, 2015	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation-related costs		$ 4,200	$ 0	$ 0	$ 4,232
Chief Executive Officer
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation-related costs		3,100
Fair value of fully-vested restricted stock unit award		2,000
Compensation	$ 1,100
Recruitment and other professional fees		$ 1,100

Restructuring Charges, net (Det

Restructuring Charges, net (Details) - 2014 Restructuring plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Restructuring charges (credit), net	$ 0	$ 0	$ (972)	$ 14,200
Employee termination benefits
Restructuring Cost and Reserve [Line Items]
Restructuring charges (credit), net				13,900
Lease exit costs
Restructuring Cost and Reserve [Line Items]
Restructuring charges (credit), net				$ 300

Earnings Per Share (Narrative)

Earnings Per Share (Narrative) (Details) - shares shares in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Potential common share excluded from computation of diluted earnings per share (shares)	1	1	1

Earnings Per Share (Computation

Earnings Per Share (Computation Of Basic And Diluted Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net income attributable to Sotheby's	$ 76,709	$ (23,479)	$ 76,891	$ (11,325)	$ 65,502	$ (23,479)	$ 88,964	$ (25,884)	$ 118,796	$ 74,112	$ 43,727
Less: Net income attributable to participating securities									1,765	1,001	354
Net income attributable to Sotheby's common shareholders									$ 117,031	$ 73,111	$ 43,373
Denominator:
Weighted average basic shares outstanding (shares)	52,471	52,532	52,716	53,016	52,956	55,013	57,104	63,022	52,684	57,024	68,121
Basic earnings per share - Sotheby's common shareholders (usd per share)	$ 1.44	$ (0.45)	$ 1.44	$ (0.21)	$ 1.22	$ (0.99)	$ 1.54	$ (0.41)	$ 2.22	$ 1.28	$ 0.64
Numerator:
Net income (loss) attributable to Sotheby's	$ 76,709	$ (23,479)	$ 76,891	$ (11,325)	$ 65,502	$ (23,479)	$ 88,964	$ (25,884)	$ 118,796	$ 74,112	$ 43,727
Less: Net income attributable to participating securities									1,765	1,001	354
Net income attributable to Sotheby's common shareholders									$ 117,031	$ 73,111	$ 43,373
Denominator:
Weighted average common shares outstanding (shares)	52,471	52,532	52,716	53,016	52,956	55,013	57,104	63,022	52,684	57,024	68,121
Weighted average effect of dilutive potential common shares:
Performance share units (shares)									231	465	438
Deferred stock units (shares)									161	149	167
Stock options (shares)									25	15	18
Weighted average dilutive potential common shares outstanding (shares)									417	629	623
Denominator for calculation of diluted earnings per share (shares)	52,853	52,532	53,054	53,016	53,685	55,013	57,712	63,022	53,101	57,653	68,744
Diluted earnings (loss) per share - Sotheby’s common shareholders (usd per share)	$ 1.43	$ (0.45)	$ 1.43	$ (0.21)	$ 1.20	$ (0.99)	$ 1.52	$ (0.41)	$ 2.20	$ 1.27	$ 0.63

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($)	Oct. 04, 2016	Oct. 03, 2016	Aug. 13, 2015	Nov. 30, 2015	Aug. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2017
Related Party Transaction [Line Items]
Auction commission revenues						$ 5,200,000	$ 4,100,000	$ 2,700,000
Related party client payable						996,197,000	511,876,000		$ 996,197,000
Accounts Receivable (net)						$ 0	$ 1,800,000		$ 0
Treasury stock acquired (in shares)		2,050,000	2,667,378	1,038,280	3,705,658	961,000	13,144,000	3,706,000	17,811,000
Aggregate purchase price			$ 100,000,000			$ 44,495,000	$ 359,885,000	$ 125,000,000	$ 529,380,000
Cost per share of stock acquired (usd per share)		$ 36	$ 37.49		$ 33.73	$ 46.32	$ 27.38	$ 33.73	$ 29.72
Ownership percentage in Sotheby's outstanding Common Stock prior to sale		8.50%
Marcato Capital Management | Sale of stock
Related Party Transaction [Line Items]
Treasury stock acquired (in shares)	2,050,000
Aggregate purchase price	$ 73,800,000
Cost per share of stock acquired (usd per share)	$ 36
Ownership percentage in Sotheby's outstanding Common Stock prior to sale		8.50%
Related party consignors
Related Party Transaction [Line Items]
Related party client payable						$ 400,000	$ 3,600,000		$ 400,000

Recently Issued Accounting S131

Recently Issued Accounting Standards (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Agency commissions and fees	$ 292,630	$ 72,650	$ 276,807	$ 99,493	$ 265,719	$ 51,285	$ 273,764	$ 81,065	$ 741,580	$ 671,833	$ 791,920
Total revenues	315,560	171,394	314,898	187,537	308,689	91,492	298,665	106,531	989,389	805,377	961,494
Agency direct costs									82,142	73,324	91,919
Total expenses									819,054	682,761	759,773
Net income attributable to Sotheby's	$ 76,709	$ (23,479)	$ 76,891	$ (11,325)	$ 65,502	$ (23,479)	$ 88,964	$ (25,884)	118,796	74,112	$ 43,727
ASU 2014-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Agency commissions and fees									809,719	724,398
Total revenues									1,057,528	857,942
Agency direct costs									150,281	125,889
Total expenses									887,193	735,326
Net income attributable to Sotheby's									118,796	74,112
ASU 2014-09 | Adjustment
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Agency commissions and fees									68,139	52,565
Total revenues									68,139	52,565
Agency direct costs									68,139	52,565
Total expenses									68,139	52,565
Net income attributable to Sotheby's									$ 0	$ 0

Quarterly Results (Unaudited132

Quarterly Results (Unaudited) (Details) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017USD ($)principal_selling_season$ / sharesshares	Sep. 30, 2017USD ($)$ / sharesshares	Jun. 30, 2017USD ($)$ / sharesshares	Mar. 31, 2017USD ($)$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Sep. 30, 2016USD ($)$ / sharesshares	Jun. 30, 2016USD ($)$ / sharesshares	Mar. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2017USD ($)principal_selling_season$ / sharesshares	Dec. 31, 2016USD ($)$ / sharesshares	Dec. 31, 2015USD ($)$ / sharesshares
Quarterly Financial Information Disclosure [Abstract]
Number of principal selling seasons | principal_selling_season	2								2
Q2 and Q4 Net Auction Sales as Percentage of Total Net Auction Sales									80.00%	82.00%
Auction Commission Revenues As Percentage Of Total Revenues									66.00%	75.00%
Net Auction Sales	$ 1,511,836	$ 286,722	$ 1,543,331	$ 474,903	$ 1,337,211	$ 160,208	$ 1,567,495	$ 491,176
Agency commissions and fees	292,630	72,650	276,807	99,493	265,719	51,285	273,764	81,065	$ 741,580	$ 671,833	$ 791,920
Inventory sales	6,167	81,501	19,937	71,377	26,429	24,359	5,281	6,794	178,982	62,863	108,699
Finance	13,114	11,697	13,359	12,767	12,073	11,138	14,750	14,755	50,937	52,716	50,489
Other	3,649	5,546	4,795	3,900	4,468	4,710	4,870	3,917	17,890	17,965	10,386
Total revenues	315,560	171,394	314,898	187,537	308,689	91,492	298,665	106,531	989,389	805,377	961,494
Operating income (loss)	107,575	(39,784)	115,398	(12,854)	91,396	(66,874)	130,083	(31,989)	170,335	122,616	201,721
Net income (loss) attributable to Sotheby's	$ 76,709	$ (23,479)	$ 76,891	$ (11,325)	$ 65,502	$ (23,479)	$ 88,964	$ (25,884)	$ 118,796	$ 74,112	$ 43,727
Basic earnings (loss) per share - Sotheby’s common shareholders (usd per share) | $ / shares	$ 1.44	$ (0.45)	$ 1.44	$ (0.21)	$ 1.22	$ (0.99)	$ 1.54	$ (0.41)	$ 2.22	$ 1.28	$ 0.64
Diluted earnings (loss) per share - Sotheby’s common shareholders (usd per share) | $ / shares	$ 1.43	$ (0.45)	$ 1.43	$ (0.21)	$ 1.20	$ (0.99)	$ 1.52	$ (0.41)	$ 2.20	$ 1.27	$ 0.63
Weighted average basic shares outstanding (shares) | shares	52,471	52,532	52,716	53,016	52,956	55,013	57,104	63,022	52,684	57,024	68,121
Weighted average diluted shares outstanding (shares) | shares	52,853	52,532	53,054	53,016	53,685	55,013	57,712	63,022	53,101	57,653	68,744

Valuation and Qualifying Acc133

Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Receivables
Valuation reserve deducted in the balance sheet from the asset to which it applies:
Balance at Beginning of Period	$ 8,940	$ 10,099	$ 8,484
Charged to Costs and Expenses	2,679	928	2,607
Charged to Other Accounts	0	0	0
Deductions	119	2,087	992
Balance at End of Period	11,500	8,940	10,099
Deferred tax assets
Valuation reserve deducted in the balance sheet from the asset to which it applies:
Balance at Beginning of Period	2,819	2,437	2,224
Charged to Costs and Expenses	384	526	461
Charged to Other Accounts	0	0	0
Deductions	9	144	248
Balance at End of Period	$ 3,194	$ 2,819	$ 2,437