Sotheby's (BID) 10-Q 3 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Oct. 31, 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-Q
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Amendment Flag	false
Entity Common Stock, Shares Outstanding		52,503,235

CONDENSED CONSOLIDATED STATEMEN

CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (UNAUDITED) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues:
Agency commissions and fees	$ 72,650	$ 51,285	$ 448,950	$ 406,114
Inventory sales	81,501	24,359	172,815	36,434
Finance	11,697	11,138	37,823	40,643
Other	5,546	4,710	14,241	13,497
Total revenues	171,394	91,492	673,829	496,688
Expenses:
Agency direct costs	10,321	5,142	49,719	45,924
Cost of inventory sales	78,734	29,616	172,396	47,735
Cost of finance revenues	6,054	4,433	16,169	12,980
Marketing	5,933	4,099	17,795	13,520
Salaries and related	61,946	70,471	213,589	213,869
General and administrative	42,483	39,355	124,796	115,940
Depreciation and amortization	5,707	5,426	16,767	16,214
Voluntary separation incentive programs (net)	0	(176)	(162)	(714)
Total expenses	211,178	158,366	611,069	465,468
Operating (loss) income	(39,784)	(66,874)	62,760	31,220
Interest income	278	295	902	966
Interest expense	(8,067)	(7,549)	(23,172)	(22,733)
Non-operating income	1,858	633	2,399	1,054
(Loss) income before taxes	(45,715)	(73,495)	42,889	10,507
Income tax (benefit) expense	(21,328)	(17,775)	2,848	3,794
Equity in earnings of investees	901	1,220	2,034	1,807
Net (loss) income	(23,486)	(54,500)	42,075	8,520
Less: Net loss attributable to noncontrolling interest	(7)	(30)	(12)	(90)
Net (loss) income attributable to Sotheby's	$ (23,479)	$ (54,470)	$ 42,087	$ 8,610
Basic (loss) earnings per share - Sotheby’s common shareholders (in dollars per share)	$ (0.45)	$ (0.99)	$ 0.79	$ 0.15
Diluted (loss) earnings per share - Sotheby's common shareholders (in dollars per share)	$ (0.45)	$ (0.99)	$ 0.78	$ 0.14
Weighted average basic shares outstanding (in shares)	52,532	55,013	52,755	58,379
Weighted average diluted shares outstanding (in shares)	52,532	55,013	53,183	58,975
Cash dividends declared per common share (in dollars per share)	$ 0	$ 0	$ 0	$ 0

CONDENSED CONSOLIDATED STATEME3

CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME (UNAUDITED) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Net (loss) income	$ (23,486)	$ (54,500)	$ 42,075	$ 8,520
Other comprehensive income (loss):
Currency translation adjustments	3,437	(4,541)	11,788	(22,627)
Defined benefit pension plan	219	0	642	81
Total other comprehensive income (loss)	3,155	1,122	10,727	(17,546)
Comprehensive (loss) income	(20,331)	(53,378)	52,802	(9,026)
Less: Comprehensive loss attributable to noncontrolling interests	(7)	(30)	(12)	(90)
Comprehensive (loss) income attributable to Sotheby's	(20,324)	(53,348)	52,814	(8,936)
Cash flow hedges
Other comprehensive income (loss):
Hedges	410	1,340	1,286	(5,096)
Net investment hedges
Other comprehensive income (loss):
Hedges	$ (911)	$ 4,323	$ (2,989)	$ 10,096

CONDENSED CONSOLIDATED BALANCE

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Current assets:
Cash and cash equivalents	$ 311,298	$ 496,031	$ 405,847
Restricted cash	5,548	59,106	6,900
Accounts receivable, net of allowance for doubtful accounts of $8,487, $7,670, and $7,834	453,906	433,614	441,457
Notes receivable, net of allowance for credit losses of $1,295, $1,270, and $1,302	51,524	37,977	72,713
Inventory (See Note 9)	63,319	159,043	179,564
Income tax receivables	25,312	6,475	16,790
Prepaid expenses and other current assets (see Note 10)	55,523	76,607	65,866
Total current assets	966,430	1,268,853	1,189,137
Notes receivable	558,342	651,159	601,170
Fixed assets, net of accumulated depreciation and amortization of $223,856, $209,196, and $209,212	350,470	347,182	347,235
Goodwill	50,496	50,029	47,833
Intangible assets (net)	11,987	13,393	13,914
Income tax receivables	4,942	686	872
Deferred income taxes	7,926	7,700	6,982
Other long-term assets (see Note 10)	196,082	165,424	150,538
Total assets	2,146,675	2,504,426	2,357,681
Current liabilities:
Client payables	376,108	511,876	389,287
Related party client payables (see Note 20)	0	0	882
Accounts payable and accrued liabilities	88,107	85,995	94,374
Accrued salaries and related costs	57,092	68,387	57,965
Current portion of York Property Mortgage (net)	11,912	6,629	6,546
Accrued income taxes	13,395	26,912	9,887
Other current liabilities (see Notes 8 and 9)	10,990	43,176	46,403
Total current liabilities	557,604	742,975	605,344
Credit facility borrowings	434,000	565,000	553,000
Long-term debt (net)	557,190	598,941	600,485
Accrued income taxes	15,816	16,600	17,519
Deferred income taxes	10,377	10,228	18,399
Other long-term liabilities (see Note 10)	51,667	65,080	47,792
Total liabilities	1,626,654	1,998,824	1,842,539
Commitments and contingencies (see Note 14)
Shareholders’ equity:
Common stock, $0.01 par value, Authorized shares — 200,000,000, Issued shares —70,777,023; 70,378,873; and 70,373,836, Outstanding shares —52,503,235; 52,971,232; and 55,017,175	709	703	703
Additional paid-in capital	446,017	444,611	439,250
Treasury stock shares, at cost — 18,273,788; 17,407,641; and 15,356,661	(550,249)	(509,885)	(436,084)
Retained earnings	702,990	660,347	594,845
Accumulated other comprehensive loss	(79,631)	(90,358)	(83,750)
Total shareholders’ equity	519,836	505,418	514,964
Noncontrolling interest	185	184	178
Total equity	520,021	505,602	515,142
Total liabilities and shareholders’ equity	$ 2,146,675	$ 2,504,426	$ 2,357,681

CONDENSED CONSOLIDATED BALANCE5

CONDENSED CONSOLIDATED BALANCE SHEETS (UNAUDITED) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Statement of Financial Position [Abstract]
Allowance for doubtful accounts	$ 8,487	$ 7,670	$ 7,834
Allowance for credit losses	1,295	1,270	1,302
Accumulated depreciation and amortization	$ 223,856	$ 209,196	$ 209,212
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01	$ 0.01
Authorized shares (in shares)	200,000,000	200,000,000	200,000,000
Issued shares (in shares)	70,777,023	70,378,873	70,373,836
Outstanding shares (in shares)	52,503,235	52,971,232	55,017,175
Treasury stock shares (in shares)	18,273,788	17,407,641	15,356,661

CONDENSED CONSOLIDATED STATEME6

CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating Activities:
Net income attributable to Sotheby's	$ 42,087	$ 8,610
Adjustments to reconcile net income attributable to Sotheby's to net cash used by operating activities:
Depreciation and amortization	16,767	16,214
Deferred income tax expense (benefit)	9,396	(16,944)
Share-based payments	17,423	10,048
Net pension benefit	(3,719)	(5,025)
Inventory writedowns and bad debt provisions	9,127	11,712
Amortization of debt discount and issuance costs	1,240	1,205
Equity in earnings of investees	(2,034)	(1,807)
Other	683	563
Changes in assets and liabilities:
Accounts receivable	29,878	441,122
Client payables	(167,233)	(284,180)
Related party client payables (see Note 20)	0	(284,536)
Inventory	88,422	20,620
Changes in other operating assets and liabilities (see Note 11)	(115,676)	(17,452)
Net cash used by operating activities	(73,639)	(99,850)
Investing Activities:
Funding of notes receivable	(152,242)	(216,601)
Collections of notes receivable	206,899	232,027
Capital expenditures	(14,462)	(16,475)
Acquisitions, net of cash acquired (see Notes 5 and 19)	(75)	(51,844)
Funding of investments (see Note 10)	(6,169)	(2,200)
Distributions from investees	4,675	1,925
Proceeds from the sale of equity investment (see Note 4)	2,125	250
Settlement of net investment hedges (see Note 8)	29,110	(3,308)
Decrease in restricted cash	38,575	26,771
Net cash provided (used) by investing activities	108,436	(29,455)
Financing Activities:
Debt issuance and other borrowing costs	(163)	(155)
Proceeds from credit facility borrowings	31,500	102,500
Repayments of credit facility borrowings	(162,500)	(91,000)
Repayments of York Property Mortgage	(37,709)	(5,428)
Decrease (increase) in restricted cash related to York Property Mortgage (see Note 7)	2,857	(3,601)
Repurchases of common stock	(40,193)	(286,084)
Dividends paid	(2,375)	(1,743)
Funding of employee tax obligations upon the vesting of share-based payments	(16,774)	(5,779)
Net cash used by financing activities	(225,357)	(291,290)
Effect of exchange rate changes on cash and cash equivalents	5,827	(22,255)
Decrease in cash and cash equivalents	(184,733)	(442,850)
Cash and cash equivalents at beginning of period	496,031	848,697
Cash and cash equivalents at end of period	$ 311,298	$ 405,847

Basis of Presentation

Basis of Presentation	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Basis of Presentation	Basis of Presentation Accounting Principles —The unaudited Condensed Consolidated Financial Statements included herein have been prepared by the management of Sotheby’s (or the "Company") 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 Securities and Exchange Commission (the "SEC"). Certain information and footnote disclosures normally included in financial statements prepared in accordance with U.S. GAAP have been condensed or omitted from this report, as is permitted by such rules and regulations. In our opinion, the unaudited Condensed Consolidated Financial Statements reflect all adjustments of a normal recurring nature that are necessary for a fair presentation of the results for the interim periods presented. The interim results presented in our Condensed Consolidated Statements of Operations are not necessarily indicative of results for a full year. See Note 2 for information about the seasonality of our business. We urge you to read these unaudited Condensed Consolidated Financial Statements in conjunction with the information included in our 2016 Form 10-K filed with the SEC on February 27, 2017. Principles of Consolidation —The unaudited Condensed 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 Condensed Consolidated Statements of Operations and the non-controlling 20% ownership interest is reported as "Noncontrolling Interest" within the Equity section of our Condensed Consolidated Balance Sheets. Intercompany transactions and balances among our subsidiaries are eliminated in consolidation. Equity investments through which we exercise significant influence over the investee, but do not control, are accounted for using the equity method. Under the equity method, our share of investee earnings or losses is recorded within Equity in Earnings of Investees in our Condensed Consolidated Statements of Operations. Our interest in the net assets of these equity method investees is recorded within Other Long-Term Assets on our Condensed Consolidated Balance Sheets. Our equity method investees include: (i) Acquavella Modern Art ("AMA"), a partnership through which a collection of fine art is being sold, (ii) RM Sotheby's, an auction house for investment-quality automobiles, and (iii) a partnership through which artworks are being purchased and sold (see Note 10). Presentation of Salaries and Related Costs —We do not allocate salaries and related costs to our cost of revenue, marketing expense, and general and administrative expense line items, as many employees often perform duties that could be categorized across more than one of these line items. Estimates and Assumptions —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. Adoption of Accounting Standards Update ("ASU") 2016-09 —In March 2016, the Financial Accounting Standards Board (the "FASB") issued ASU 2016-09, Compensation-Stock Compensation: Improvements to Employee Share-Based Payment Accounting. ASU 2016-09 simplifies several aspects of the accounting 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 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. We adopted this aspect of ASU 2016-09 on a prospective basis beginning on January 1, 2017. The adoption of ASU 2016-09 and the vesting of certain share-based payments in the first nine months of 2017 resulted in the recording of a discrete $2.6 million income tax benefit in our Condensed Consolidated Statements of Operations, which decreased our effective income tax rate for the nine months ended September 30, 2017 by approximately 6% . Under previous guidance, this income tax benefit would have been recorded as an increase to Additional Paid-In Capital on our Condensed 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. The adoption of ASU 2016-09 in the first quarter of 2017 resulted in the classification of $2.6 million of excess tax benefits within Operating Activities in our Condensed Consolidated Statement of Cash Flows for the nine months ended September 30, 2017 . The retrospective adoption of ASU 2016-09 did not have an effect on our Condensed Consolidated Statement of Cash Flows for the nine months ended September 30, 2016 because no excess tax benefits were recorded in that period. The adoption of the other aspects of ASU 2016-09 did not have a material impact on our Condensed Consolidated Financial Statements as of and for the three and nine months ended September 30, 2017 and 2016 . Adoption of Other Recently Issued Accounting Standards —In March 2016, the FASB issued ASU 2016-05, Derivatives and Hedging: Effect of Derivative Contract Novations on Existing Hedge Accounting Relationships , which clarifies that a change in the counterparty to a derivative instrument that has been designated as a hedging instrument would not, in and of itself, be considered a termination of the derivative instrument, provided that all other hedge accounting criteria continue to be met. The adoption of ASU 2016-05 on its effective date of January 1, 2017 did not have a material effect on our Condensed Consolidated Financial Statements as of and for the three and nine months ended September 30, 2017 and 2016 . In March 2016, the FASB issued ASU 2016-06, Derivatives and Hedging-Contingent Put and Call Options in Debt Instruments , which aims to reduce the diversity of practice in identifying embedded derivatives in debt instruments. ASU 2016-06 clarifies that the nature of an exercise contingency is not subject to the “clearly and closely” criteria for purposes of assessing whether the call or put option must be separated from the debt instrument and accounted for separately as a derivative. The adoption of ASU 2016-06 on its effective date of January 1, 2017 did not have a material effect on our Condensed Consolidated Financial Statements as of and for the three and nine months ended September 30, 2017 and 2016 .

Seasonality of Business

Seasonality of Business	9 Months Ended
	Sep. 30, 2017
Seasonality Of Business [Abstract]
Seasonality of Business	Seasonality of Business 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 82% and 78% of our total annual Net Auction Sales for the years ended December 31, 2016 and 2015 , respectively, with auction commission revenues comprising approximately 75% of our total revenues in each of those years. 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. ___________________________________________________________________ 1 Represents the total hammer (sale) price of property sold at auction.

Segment Reporting

Segment Reporting	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Segment Reporting	Segment Reporting Sotheby's is a global art and luxury business, offering its clients opportunities to connect with and transact in the world's most extraordinary objects. Auctioneers since 1744, today we offer a variety of innovative art-related services, including the brokerage of private art sales, the brokerage of private jewelry sales through our Sotheby's Diamonds brand, exclusive private selling exhibitions at our S|2 galleries, 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 Chief Executive Officer, 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, Agency segment activities also include the sale of artworks that are principally acquired as a consequence of the auction process, and RM Sotheby's, an equity investee that operates as 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 deploys a unique combination of art expertise, 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”), 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. AAP was acquired on January 11, 2016 (see Note 19). Our advisory services are classified within All Other for segment reporting purposes, along with our retail wine business, brand licensing activities, the results from certain equity method investments (see Note 10), and sales of the remaining inventory of Noortman Master Paintings, an art dealer that was owned and operated by us from its acquisition in 2006 until its closure in December 2013. The following table presents our segment information for the three and nine months ended September 30, 2017 and 2016 (in thousands of dollars): Three Months Ended September 30, 2017 Agency SFS All Other Reconciling items (a) Total Revenues $ 152,160 $ 13,781 $ 7,537 $ (2,084 ) $ 171,394 Segment (loss) income before taxes $ (55,061 ) $ 5,965 $ 4,282 $ (901 ) (b) $ (45,715 ) Three Months Ended September 30, 2016 Revenues $ 74,095 $ 13,150 $ 6,259 $ (2,012 ) $ 91,492 Segment (loss) income before taxes $ (77,455 ) $ 7,087 $ (1,907 ) $ (1,220 ) (b) $ (73,495 ) Nine Months Ended September 30, 2017 Revenues $ 615,092 $ 44,514 $ 20,914 $ (6,691 ) $ 673,829 Segment income before taxes $ 13,743 $ 22,177 $ 9,003 $ (2,034 ) (b) $ 42,889 Nine Months Ended September 30, 2016 Revenues $ 436,928 $ 46,182 $ 19,117 $ (5,539 ) $ 496,688 Segment (loss) income before taxes $ (17,031 ) $ 28,027 $ 1,318 $ (1,807 ) (b) $ 10,507 (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 (loss) income before taxes are detailed in the table below. The table below presents a reconciliation of segment (loss) income before taxes to consolidated (loss) income before taxes for the three and nine months ended September 30, 2017 and 2016 (in thousands of dollars): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Agency $ (55,061 ) $ (77,455 ) $ 13,743 $ (17,031 ) SFS 5,965 7,087 22,177 28,027 All Other 4,282 (1,907 ) 9,003 1,318 Segment (loss) income before taxes (44,814 ) (72,275 ) 44,923 12,314 Reconciling items: Equity in earnings of investees (a) (901 ) (1,220 ) (2,034 ) (1,807 ) (Loss) income before taxes $ (45,715 ) $ (73,495 ) $ 42,889 $ 10,507 (a) For segment reporting purposes, our share of earnings related to equity investees is included as part of (loss) income before taxes. However, such earnings are reported separately below (loss) income before taxes in our Condensed Consolidated Statements of Operations. The table below presents segment assets, as well as a reconciliation of segment assets to consolidated assets as of September 30, 2017 , December 31, 2016 , and September 30, 2016 (in thousands of dollars): September 30, 2017 December 31, 2016 September 30, 2016 Agency $ 1,441,249 $ 1,759,670 $ 1,608,803 SFS 627,815 687,649 683,331 All Other 39,431 42,246 40,903 Total segment assets 2,108,495 2,489,565 2,333,037 Unallocated amounts and reconciling items: Deferred tax assets and income tax receivable 38,180 14,861 24,644 Consolidated assets $ 2,146,675 $ 2,504,426 $ 2,357,681 Substantially all of our capital expenditures for the nine months ended September 30, 2017 , the year ended December 31, 2016 , and the nine months ended September 30, 2016 were attributable to the Agency segment.

Receivables

Receivables	9 Months Ended
	Sep. 30, 2017
Receivables [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 our commission, 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. 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 from 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 to Notes Receivable on our Condensed Consolidated Balance Sheets. As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , Notes Receivable within the Agency segment included $2.7 million , $7.5 million , and $10.2 million , respectively, of such balances that have been reclassified from Accounts Receivable. 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 may be cancelled, and the property will be 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 September 30, 2017 , December 31, 2016 , and September 30, 2016 , Accounts Receivable (net) included $144.9 million , $90.1 million , and $138 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 September 30, 2017 , December 31, 2016 , and September 30, 2016 , Accounts Receivable (net) also included $16.4 million , $76.3 million , and $13 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 and/or purchases. 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 primarily funded with borrowings drawn from a dedicated revolving credit facility. To a lesser extent, cash balances are also used to fund a portion of the loans made by SFS, as appropriate. See Note 7 for information related to the dedicated revolving credit facility for SFS. As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , the net Notes Receivable balance of SFS was $602.2 million , $675.1 million , and $655.2 million , respectively. As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , the total net Notes Receivable balance of SFS included $57.9 million , $88.7 million , and $90.4 million , respectively, of term loans issued by SFS to refinance client auction and private sale purchases. For the nine months ended September 30, 2017 and 2016 , SFS issued $6.5 million and $11.7 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 Condensed Consolidated Statements of Cash Flows. Upon repayment, the cash received in settlement of such Notes Receivable is classified within Operating Activities in our Condensed Consolidated Statements of Cash Flows. For the nine months ended September 30, 2017 and 2016 , such repayments totaled $37.3 million and $30.1 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 of 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 the 50% target due to a decrease in the low auction estimates 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 September 30, 2017 , December 31, 2016 , and September 30, 2016 (in thousands of dollars): September 30, December 31, September 30, Secured loans $ 602,176 $ 675,109 $ 655,152 Low auction estimate of collateral $ 1,378,737 $ 1,405,856 $ 1,347,334 Aggregate LTV ratio 44 % 48 % 49 % The table below provides the aggregate LTV ratio for secured loans made by SFS with an LTV ratio above 50% as of September 30, 2017 , December 31, 2016 , and September 30, 2016 (in thousands of dollars): September 30, December 31, September 30, Secured loans with an LTV ratio above 50% $ 179,568 $ 270,111 $ 354,698 Low auction estimate of collateral related to secured loans with an LTV ratio above 50% $ 306,603 $ 486,973 $ 646,259 Aggregate LTV ratio of secured loans with an LTV ratio above 50% 59 % 55 % 55 % The table below provides other credit quality information regarding secured loans made by SFS as of September 30, 2017 , December 31, 2016 , and September 30, 2016 (in thousands of dollars): September 30, December 31, September 30, Total secured loans $ 602,176 $ 675,109 $ 655,152 Loans past due $ 79,038 $ 90,508 $ 17,204 Loans more than 90 days past due $ 78,367 $ 158 $ 926 Non-accrual loans $ — $ 158 $ 167 Impaired loans $ — $ — $ — Allowance for credit losses: Allowance for credit losses for impaired loans $ — $ — $ — Allowance for credit losses based on historical data 1,295 1,270 1,302 Total allowance for credit losses - secured loans $ 1,295 $ 1,270 $ 1,302 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 obligations. As of September 30, 2017 , $79 million of the net Notes Receivable balance was past due, of which $78.4 million was more than 90 days past due. As of September 30, 2017, the collateral securing these past due loans had a low auction estimate of approximately $183.4 million resulting in an LTV ratio of approximately 43% . As of September 30, 2017, we are continuing to accrue interest on all past due loans. In consideration of expected loan renewals, loan payments, and $12 million in collateral sales to date related to loans that are more than 90 days past due for which the proceeds have not yet been collected from the buyer, as well as the value of the remaining collateral and our current collateral disposal plans, we believe that the principal and interest amounts owed for these past due 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 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. As of September 30, 2017 , there were no non-accrual loans outstanding. As of December 31, 2016 and September 30, 2016 , there was a $0.2 million non-accrual loan outstanding. This loan was written-off in the second quarter of 2017. 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 September 30, 2017 , December 31, 2016 , and September 30, 2016 , there were no impaired loans outstanding. During the period January 1, 2017 to September 30, 2017 , activity related to the Allowance for Credit Losses was as follows (in thousands of dollars): Allowance for credit losses as of January 1, 2017 $ 1,270 Change in loan loss provision 25 Allowance for credit losses as of September 30, 2017 $ 1,295 As of September 30, 2017 , unfunded commitments to extend additional credit through SFS were approximately $52.4 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 Condensed Consolidated Balance Sheets within Notes Receivable (net). As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , there were $1.1 million , $1 million , and $2.3 million of auction guarantee advances outstanding, respectively. See Note 16 for additional 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 Condensed Consolidated Balance Sheets. As of September 30, 2017 and December 31, 2016 , Notes Receivable (net) within the Agency segment included $2.7 million and $7.5 million , respectively, of such amounts reclassified from Accounts Receivable (net), against which we hold approximately $3.1 million of collateral. As of September 30, 2016 , Notes Receivable (net) within the Agency segment included $10.2 million of such reclassified amounts, against which we held $4.4 million of collateral. 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 Condensed Consolidated Statements of Cash Flows. Upon repayment, the cash received in settlement of such Notes Receivable is classified within Operating Activities in our Condensed Consolidated Statements of Cash Flows. For the nine months ended September 30, 2017 and 2016, such repayments totaled $5 million and $13.7 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 September 30, 2017 , December 31, 2016 , and September 30, 2016 , such loans totaled $3.8 million , $3.8 million , and $4.1 million , respectively. We are no longer accruing interest with respect to one of these loans with a balance of $2.1 million , but management believes that this balance 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 and September 30, 2016 , the carrying value of this loan was approximately $2.1 million and $2.2 million , respectively. The entire remaining balance of the loan was repaid in the second quarter of 2017.

Goodwill and Intangible Assets

Goodwill and Intangible Assets	9 Months Ended
	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill and Intangible Assets	Goodwill and Intangible Assets Goodwill —For the nine months ended September 30, 2017 and 2016 , changes in the carrying value of Goodwill were as follows (in thousands of dollars): Nine Months Ended September 30, 2017 Nine Months Ended September 30, 2016 Agency All Other Total Agency All Other Total Beginning balance as of December 31 $ 43,878 $ 6,151 $ 50,029 $ 13,621 $ — $ 13,621 Goodwill acquired (see Note 19) — — — 28,339 6,151 34,490 Foreign currency exchange rate changes 467 — 467 (278 ) — (278 ) Ending balance as of September 30 $ 44,345 $ 6,151 $ 50,496 $ 41,682 $ 6,151 $ 47,833 Intangible Assets —As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , intangible assets consisted of the following (in thousands of dollars): Amortization Period September 30, 2017 December 31, 2016 September 30, Indefinite lived intangible assets: License (a) N/A $ 324 $ 324 $ 324 Intangible assets subject to amortization: Customer relationships - AAP (see Note 19) 8 years 10,800 10,800 10,800 Non-compete agreements - AAP (see Note 19) 6 years 3,060 3,060 3,060 Artworks database (b) 10 years 1,200 1,125 1,125 Total intangible assets subject to amortization 15,060 14,985 14,985 Accumulated amortization (3,397 ) (1,916 ) (1,395 ) Total amortizable intangible assets (net) 11,663 13,069 13,590 Total intangible assets (net) $ 11,987 $ 13,393 $ 13,914 (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 along 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 three and nine months ended September 30, 2017 , amortization expense related to intangible assets was approximately $0.5 million and $1.5 million , respectively. For the three and nine months ended September 30, 2016 , amortization expense related to intangible assets was approximately $0.5 million and $1.4 million , respectively. The estimated aggregate amortization expense for the remaining useful lives of intangible assets subject to amortization during the five -year period succeeding the September 30, 2017 balance sheet date are as follows (in thousands of dollars): Period Amount October 2017 to September 2018 $ 1,981 October 2018 to September 2019 $ 1,981 October 2019 to September 2020 $ 1,981 October 2020 to September 2021 $ 1,981 October 2021 to September 2022 $ 1,598

Defined Benefit Pension Plan

Defined Benefit Pension Plan	9 Months Ended
	Sep. 30, 2017
Retirement Benefits [Abstract]
Defined Benefit Pension Plan	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 a defined contribution plan. For the three and nine months ended September 30, 2017 and 2016 , the components of the net credits related to the U.K. Pension Plan were as follows (in thousands of dollars): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Service cost $ — $ — $ — $ 1,153 Interest cost 2,047 2,385 5,984 7,600 Expected return on plan assets (3,598 ) (4,324 ) (10,519 ) (13,778 ) Prior service cost 15 — 45 — Amortization of actuarial loss 289 — 842 — Amortization of prior service cost (25 ) — (71 ) — Net pension credit $ (1,272 ) $ (1,939 ) $ (3,719 ) $ (5,025 )

Debt

Debt	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Debt	Debt Revolving Credit Facilities —We are party to a credit agreement with an international syndicate of lenders, which provides for separate 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 the working capital and other general corporate needs of each segment, 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 September 27, 2017, we provided notice to our lenders to reduce the borrowing capacity of the SFS Credit Facility by $235 million , effective October 2, 2017. This reduction, which was entirely at our option and part of an ongoing commitment to allocate capital wisely, was executed in order to reduce facility fees for borrowing capacity that cannot be used due to secured debt limits under our $300 million 5.25% Senior Notes. 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, 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 upon a percentage of the carrying value of certain SFS loans (see Note 4 ) and the fair value of certain of our trademarks. The obligations under the Credit Agreements 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, a $600 million limitation on net outstanding auction guarantees (i.e., auction guarantees less the impact of related risk and reward sharing arrangements), and limitations on the use of proceeds from borrowings under the Credit Agreement. 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 September 30, 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 September 30, 2017 , $5.6 million of such unamortized fees are included within Other Long-Term Assets on our Condensed Consolidated Balance Sheets. The following tables summarize information related to the Credit Agreement as of and for the periods ended September 30, 2017 , December 31, 2016 , and September 30, 2016 (in thousands of dollars): As of and for the three and nine months ended September 30, 2017 Agency Credit Facility SFS Credit Facility Total Maximum borrowing capacity (a) $ 300,000 $ 1,035,000 (a) $ 1,335,000 (a) Borrowing base $ 134,936 $ 503,132 $ 638,068 Borrowings outstanding $ — $ 434,000 $ 434,000 Available borrowing capacity (a) (b) $ 134,936 $ 69,132 $ 204,068 Average Borrowings Outstanding: Three months ended September 30, 2017 $ — $ 508,342 $ 508,342 Nine months ended September 30, 2017 $ — $ 537,374 $ 537,374 Borrowing Costs - Three Months Ended September 30, 2017: Interest $ — (c) $ 4,746 (d) $ 4,746 Fees 777 (c) 1,308 (d) 2,085 Total $ 777 $ 6,054 $ 6,831 Borrowing Costs - Nine Months Ended September 30, 2017: Interest $ — (c) $ 13,471 (d) $ 13,471 Fees 2,141 (c) 2,698 (d) 4,839 Total $ 2,141 $ 16,169 $ 18,310 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 (b) $ 165,443 $ 4,021 $ 169,464 Average borrowings outstanding $ — $ 534,433 $ 534,433 As of and for the three and nine months ended September 30, 2016 Agency Credit Facility SFS Credit Facility Total Maximum borrowing capacity $ 300,000 $ 1,035,000 $ 1,335,000 Borrowing base $ 174,548 $ 554,969 $ 729,517 Borrowings outstanding $ — $ 553,000 $ 553,000 Available borrowing capacity (b) $ 174,548 $ 1,969 $ 176,517 Average Borrowings Outstanding: Three months ended September 30, 2016 $ — $ 523,397 $ 523,397 Nine months ended September 30, 2016 $ — $ 527,204 $ 527,204 Borrowing Costs - Three Months Ended September 30, 2016: Interest $ — (c) $ 3,694 (d) $ 3,694 Fees 640 (c) 739 (d) 1,379 Total $ 640 $ 4,433 $ 5,073 Borrowing Costs - Nine Months Ended September 30, 2016: Interest $ — (c) $ 10,824 (d) $ 10,824 Fees 2,028 (c) 2,156 (d) 4,184 Total $ 2,028 $ 12,980 $ 15,008 (a) As discussed above, on September 27, 2017, we provided notice to our lenders to reduce the borrowing capacity of the SFS Credit Facility by $235 million , effective October 2, 2017. (b) The available borrowing capacity is calculated as the borrowing base less borrowings outstanding. (c) Borrowing costs related to the Agency Credit Facility, which include interest and fees, are reflected in our Condensed Consolidated Statements of Operations as Interest Expense. (d) Borrowing costs related to the SFS Credit Facility are reflected in our Condensed Consolidated Statements of Operations within Cost of Finance Revenues. For the three and nine months ended September 30, 2017 , the weighted average cost of borrowings related to the SFS Credit Facility was approximately 4.8% and 4.0% , respectively. For the three and nine months ended September 30, 2017 , 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. Excluding this charge, the weighted average cost of borrowings related to the SFS Credit Facility was approximately 4.2% and 3.8% for the three and nine months ended September 30, 2017, respectively. For the three and nine months ended September 30, 2016, the weighted average cost of borrowings related to the SFS Credit Facility was approximately 3.4% and 3.3% , respectively. Long-Term Debt —As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , Long-Term Debt consisted of the following (in thousands of dollars): September 30, December 31, September 30, York Property Mortgage, net of unamortized debt issuance costs of $4,797, $5,555, and $5,808 $ 272,261 $ 309,212 $ 310,834 2022 Senior Notes, net of unamortized debt issuance costs of $3,159, $3,642, and $3,803 296,841 296,358 296,197 Less current portion: York Property Mortgage, net of unamortized debt issuance costs of $1,010, $1,010, and $1,010 (11,912 ) (6,629 ) (6,546 ) Total Long-Term Debt, net $ 557,190 $ 598,941 $ 600,485 See the captioned sections below for information related to the York Property Mortgage and the 2022 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, including S|2, our private sale exhibition gallery. 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 share repurchases. As of September 30, 2017, Sotheby's net worth was $520 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 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 a restricted cash management account associated with the York Property Mortgage. Any prepayments made during the period July 2018 to July 2021 will also be funded exclusively 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 8 for information related to these interest 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 Condensed 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, our 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 monthly 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 September 30, 2017 , December 31, 2016 , and September 30, 2016 , the Cash Management Account had a balance of $1.8 million , $4.6 million , and $3.6 million , respectively, which is reflected within Restricted Cash on our Condensed Consolidated Balance Sheets. • Sotheby's is required to maintain a net worth of at least $325 million , subject to a cure period. As of September 30, 2017 , the fair value of the York Property Mortgage approximated its book value due to the variable interest rate associated with the mortgage. The fair value measurement is considered to be a Level 2 fair value measurement in the fair value hierarchy as per ASC 820, Fair Value Measurements . 2022 Senior Notes —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. The 2022 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. Interest on the 2022 Senior Notes is payable semi-annually in cash on April 1 and October 1 of each year. As of September 30, 2017 , the $300 million principal amount of the 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. Future Principal and Interest Payments —The aggregate future principal and interest payments due under the Credit Agreement, the York Property Mortgage, and the 2022 Senior Notes during the five-year period after September 30, 2017 are as follows (in thousands of dollars): Period Amount October 2017 to September 2018 $ 38,233 October 2018 to September 2019 $ 37,494 October 2019 to September 2020 $ 471,953 October 2020 to September 2021 $ 38,567 October 2021 to September 2022 $ 244,850 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 prepayments in reference to available forecasts of LIBOR rates for the future periods through maturity.

Derivative Financial Instrument

Derivative Financial Instruments	9 Months Ended
	Sep. 30, 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 that we have designated as hedging instruments as of September 30, 2017 , December 31, 2016 , and September 30, 2016 (in thousands of dollars): Assets Liabilities September 30, 2017 Balance Sheet Classification Fair Value Balance Sheet Classification Fair Value Cash Flow Hedges: Interest rate swap Other Current Assets $ 238 N/A $ — Interest rate collar N/A — Other Current Liabilities 1,375 Interest rate collar N/A — Other Long-Term Liabilities 2,900 Total cash flow hedges 238 — 4,275 Net Investment Hedges: Foreign exchange contracts N/A — Other Current Liabilities 3,626 Total $ 238 $ 7,901 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 Assets Liabilities September 30, 2016 Balance Sheet Classification Fair Value Balance Sheet Classification Fair Value Cash Flow Hedges: Interest rate swap N/A $ — Other Current Liabilities $ 651 Interest rate collar N/A — Other Long-Term Liabilities 14,696 Total cash flow hedges — 15,347 Net Investment Hedges: Foreign exchange contracts Other Current Assets 20,098 Other Current Liabilities — Total $ 20,098 $ 15,347 During the nine months ended September 30, 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 Condensed Consolidated Balance Sheets within Accumulated Other Comprehensive Loss. The following tables summarize the effect of the derivative financial instruments that we have designated as hedging instruments on our Condensed Consolidated Statements of Operations and Condensed Consolidated Statements of Comprehensive (Loss) Income for the three and nine months ended September 30, 2017 and 2016 (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 (Loss) Income Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Effective Portion Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Ineffective Portion Three Months Ended September 30, 2017 2016 2017 2016 2017 2016 Cash Flow Hedges: Interest rate swaps $ (7 ) $ 223 Interest Expense $ (8 ) $ 192 $ — $ — Interest rate collar 125 925 Interest Expense 300 — — — Total cash flow hedges 118 1,148 292 192 — — Net Investment Hedges: Foreign exchange contracts (911 ) 4,323 N/A — — — — Total $ (793 ) $ 5,471 $ 292 $ 192 $ — $ — 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 Nine Months Ended September 30, 2017 2016 2017 2016 2017 2016 Cash Flow Hedges: Interest rate swaps $ 127 $ (860 ) Interest Expense $ 27 $ 631 $ — $ — Interest rate collar 210 (4,867 ) Interest Expense 300 — — — Interest rate collar — — Non-operating income — — 622 — Total cash flow hedges 337 — (5,727 ) 327 631 622 — Net Investment Hedges: Foreign exchange contracts (2,989 ) 10,096 N/A — — — — Total $ (2,652 ) $ 4,369 $ 327 $ 631 $ 622 $ — See the captioned sections below for information related to the derivative financial instruments that we have 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 7), 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. For the three months ended September 30, 2017, 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 September 30, 2017 , the notional value of the Mortgage Collar was $277.1 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 September 30, 2017 , the notional value of the SFS Swap was $63 million . See Note 7 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 Condensed Consolidated Balance Sheets and then reclassified to Interest Expense in our Condensed Consolidated Statements of Operations in the same period that interest expense related to the underlying debt instruments is recorded. Any hedge ineffectiveness is immediately recognized in Net Income (Loss). 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 Condensed Consolidated Balance Sheets would be immediately reclassified into Net Income (Loss). 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 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 September 30, 2017, each of the 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 September 30, 2017 , the aggregate notional value of our outstanding net investment hedge contracts 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 Condensed 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 Condensed Consolidated Statements of Operations in Non-Operating Income. As of September 30, 2017 , the notional value of outstanding forward exchange contracts not designated as hedging instruments was $143.9 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 September 30, 2017 , December 31, 2016 , and September 30, 2016 , the aggregate fair value of these contracts represented liabilities of $0.4 million , $3.6 million , and $10.5 million , respectively, which were recorded on our Condensed Consolidated Balance Sheets within Accounts Payable and Accrued Liabilities.

Sale of Pink Diamond

Sale of Pink Diamond	9 Months Ended
	Sep. 30, 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 Condensed 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 , after taking into account the associated Cost of Inventory Sales of $70.8 million , which includes amounts due to our partner in the Pink Diamond and other costs related to the sale, and is recorded in our results of operations for the three and nine months ended September 30, 2017.

Supplemental Condensed Consolid

Supplemental Condensed Consolidated Balance Sheet Information	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Supplemental Condensed Consolidated Balance Sheet Information	Supplemental Condensed Consolidated Balance Sheet Information As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , Prepaid Expenses and Other Current Assets consisted of the following (in thousands of dollars): September 30, December 31, September 30, Prepaid expenses $ 31,623 $ 20,436 $ 29,716 Derivative financial instruments (see Note 8) 239 30,340 20,098 Other (a) 23,661 25,831 16,052 Total Prepaid Expenses and Other Current Assets $ 55,523 $ 76,607 $ 65,866 (a) Other principally includes receivables related to insurance recoveries and, to a much lesser extent, other miscellaneous short-term assets. For the nine months ended September 30, 2017 , we settled derivative financial instruments designated as net investment hedges with an aggregate notional value $213.8 million and realized a net gain of $29.1 million . See Note 8 for additional information related to derivative financial instruments. As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , Other Long-Term Assets consisted of the following (in thousands of dollars): September 30, December 31, September 30, Defined benefit pension plan asset (see Note 6) $ 90,559 $ 78,576 $ 63,563 Equity method investments (a) 46,207 43,143 41,695 Trust assets related to deferred compensation liability 25,325 26,713 27,962 Restricted cash (b) 17,835 1,064 1,127 Other 16,156 15,928 16,191 Total Other Long-Term Assets $ 196,082 $ 165,424 $ 150,538 (a) Includes our equity method investments in RM Sotheby's and AMA, as well as a partnership that was formed in the second quarter of 2017 through which artworks are being purchased and sold. As of September 30, 2017, our investment in this partnership was $5.4 million , representing our 50% ownership interest. (b) As of September 30, 2017, restricted cash reflected within Other Long-Term Assets principally relates to $15.3 million of funds held in escrow pending the final settlement of a sale. As of December 31, 2016 and September 30, 2016, restricted cash reflected within Other Long-Term Assets primarily consists of segregated cash related to long-term lease arrangements. As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , Other Long-Term Liabilities consisted of the following (in thousands of dollars): September 30, December 31, September 30, Deferred compensation liability $ 24,563 $ 25,914 $ 26,086 Acquisition earn-out consideration (see Note 19) 17,500 26,250 — Interest rate collar liability (see Note 8) 2,900 5,952 14,696 Other 6,704 6,964 7,010 Total Other Long-Term Liabilities $ 51,667 $ 65,080 $ 47,792

Supplemental Condensed Consol17

Supplemental Condensed Consolidated Cash Flow Information	9 Months Ended
	Sep. 30, 2017
Supplemental Cash Flow Information [Abstract]
Supplemental Condensed Consolidated Cash Flow Information	Supplemental Condensed Consolidated Cash Flow Information For the nine months ended September 30, 2017 and 2016 , changes in other operating assets and liabilities as reported in the Condensed Consolidated Statements of Cash Flows included the following (in thousands of dollars): Nine Months Ended September 30, 2017 2016 (Increase) decrease in: Prepaid expenses and other current assets $ (2,443 ) $ (7,974 ) Other long-term assets 788 10,748 Income tax receivables and deferred income tax assets (34,168 ) 11,835 Decrease in: Accrued income taxes and deferred income tax liabilities (15,156 ) (20,220 ) Accounts payable and accrued liabilities and other liabilities (64,697 ) (11,841 ) Total changes in other operating assets and liabilities $ (115,676 ) $ (17,452 )

Shareholders' Equity and Divide

Shareholders' Equity and Dividends	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Shareholders' Equity and Dividends	Shareholders' Equity and Dividends Common Stock Repurchase Program —The following table provides information regarding our common stock repurchase program for the nine months ended September 30, 2017 and 2016 (in thousands, except for per share data): Nine Months Ended September 30, 2017 September 30, 2016 Shares repurchased 866 11,093 Aggregate purchase price $ 40,193 $ 286,084 Average price per share $ 46.40 $ 25.79 On August 15, 2017 , the Board of Directors approved a $100 million increase to our share repurchase authorization, resulting in an updated aggregate share repurchase authorization of $100.03 million . There have been no share repurchases subsequent to August 15, 2017 and, as a result, our current share repurchase authorization is $100.03 million . 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. Special Dividend —On January 29, 2014, the 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 $11 million was accrued for dividend equivalents owed on share-based payments to employees, which was charged to retained earnings. For the nine months ended September 30, 2017 and 2016 , approximately $2 million and $1.4 million , respectively, of such accrued dividend equivalents were paid upon the vesting of the underlying awards.

Accumulated Other Comprehensive

Accumulated Other Comprehensive Loss	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Accumulated Other Comprehensive Loss	Accumulated Other Comprehensive Loss The following is a summary of the changes in Accumulated Other Comprehensive Loss for the three and nine months ended September 30, 2017 and 2016 (in thousands of dollars): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Currency Translation Adjustments Balance at beginning of period $ (80,327 ) $ (71,274 ) $ (89,478 ) $ (52,279 ) Other comprehensive income (loss) before reclassifications, net of tax of $851, ($4,946), $2,272, and ($7,691) 3,870 (4,895 ) 13,021 (23,890 ) Other comprehensive income (loss) 3,870 (4,895 ) 13,021 (23,890 ) Balance at end of period (76,457 ) (76,169 ) (76,457 ) (76,169 ) Cash Flow Hedges Balance at beginning of period (2,788 ) (10,742 ) (3,664 ) (4,306 ) Other comprehensive income (loss) before reclassifications, net of tax of $72, $710 , $207, and ( $3,550) 118 1,148 337 (5,727 ) Reclassifications from accumulated other comprehensive loss, net of tax of $181 , $119, $588, and $391 292 192 949 631 Other comprehensive income (loss) 410 1,340 1,286 (5,096 ) Balance at end of period (2,378 ) (9,402 ) (2,378 ) (9,402 ) Net Investment Hedges Balance at beginning of period 14,540 5,773 16,618 — Other comprehensive (loss) income before reclassifications, net of tax of ($552), $2,817, ($1,822), and $6,694 (911 ) 4,323 (2,989 ) 10,096 Other comprehensive (loss) income (911 ) 4,323 (2,989 ) 10,096 Balance at end of period 13,629 10,096 13,629 10,096 Defined Benefit Pension Plan Balance at beginning of period (14,211 ) (8,629 ) (13,834 ) (9,619 ) Currency translation adjustments (433 ) 354 (1,233 ) 1,263 Net actuarial gain, net of tax of $0, $0, $0, and ($81) — — — 81 Prior service cost amortization, net of tax of ($5), $0, ($12), and $0 (20 ) — (59 ) — Actuarial loss amortization, net of tax of $50, $0, $141, and $0 239 — 701 — Other comprehensive (loss) income (214 ) 354 (591 ) 1,344 Balance at end of period (14,425 ) (8,275 ) (14,425 ) (8,275 ) Total other comprehensive income (loss) attributable to Sotheby's 3,155 1,122 10,727 (17,546 ) Accumulated other comprehensive loss as of September 30 $ (79,631 ) $ (83,750 ) $ (79,631 ) $ (83,750 ) The following is a summary of the reclassification adjustments made to Accumulated Other Comprehensive Loss for the three and nine months ended September 30, 2017 and 2016 (in thousands of dollars): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Cash Flow Hedges Settlements $ 473 $ 311 $ 1,537 $ 1,022 Tax effect (181 ) (119 ) (588 ) (391 ) Reclassification adjustments, net of tax 292 192 949 631 Defined Benefit Pension Plan Prior service cost amortization (25 ) — (71 ) — Actuarial loss amortization 289 — 842 — Pre-tax total 264 — 771 — Tax effect (45 ) — (129 ) — Reclassification adjustments, net of tax 219 — 642 — Total reclassification adjustments, net of tax $ 511 $ 192 $ 1,591 $ 631

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 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 December 31, 2017 and January 11, 2021 . 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 $13.9 million as of September 30, 2017 . 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 statement of operations. Guarantees of Collection— A guarantee of collection is a guarantee to a consignor that, under certain conditions, Sotheby's will pay the consignor for property that has sold at auction but has not yet been paid for by the purchaser. 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 September 30, 2017, we had issued to consignors guarantees of collection for property with an aggregate pre-sale low estimate of $2.5 million . The property related to these guarantees of collection is being offered at auctions in the fourth quarter of 2017. As of November 2, 2017, our obligation under these guarantees of collection was reduced by $1.8 million as a result of amounts collected from buyers. 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, individually or in the aggregate, will have a material adverse effect on our consolidated financial condition. See Note 4 , which discusses unfunded SFS loan commitments. See Note 7 , which discusses debt commitments. See Note 15 , which discusses income tax contingencies. See Note 16 , which discusses auction guarantees. See Note 19 , which discusses our commitment to make earn-out payments to the former principals of AAP.

Uncertain Tax Positions

Uncertain Tax Positions	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Uncertain Tax Positions	Uncertain Tax Positions As of September 30, 2017 , our liability for uncertain tax positions, excluding interest and penalties, was $14.2 million , representing a net decrease of $5.3 million when compared to a liability of $19.5 million as of December 31, 2016 . 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. As of September 30, 2016 , our liability for unrecognized tax benefits, excluding interest and penalties, was $19.7 million . As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , the total amount of unrecognized tax benefits that, if recognized, would favorably affect our effective income tax rate was $3.1 million , $9.3 million , and $13.7 million , respectively. We believe it is reasonably possible that a decrease of $3 million in the balance of unrecognized tax benefits can occur within 12 months of the September 30, 2017 balance sheet date as a result of the expiration of statutes of limitations and the expected settlement of ongoing tax audits. We are subject to taxation in the U.S., as well as in various U.S. state and foreign jurisdictions. As a result, we are 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 2009. We recognize interest expense and penalties related to unrecognized tax benefits as a component of Income Tax (Benefit) Expense in our Condensed Consolidated Statements of Operations. For the nine months ended September 30, 2017 , the accrual for such interest and penalties decreased by $0.1 million . Our policy is to record interest expense related to sales, value added and other non-income based taxes as Interest Expense in our Condensed Consolidated Statements of Operations. Penalties related to such taxes are recorded as General and Administrative Expenses in our Condensed Consolidated Statements of Operations. Interest expense and penalties related to income taxes are recorded as a component of Income Tax (Benefit) Expense in our Condensed Consolidated Statements of Operations.

Auction Guarantees

Auction Guarantees	9 Months Ended
	Sep. 30, 2017
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 Condensed Consolidated Statements of Operations 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 Condensed 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 Condensed 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 fixed 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 September 30, 2017 , we had outstanding auction guarantees totaling $139.6 million . Our financial exposure under these auction guarantees is reduced by irrevocable bids totaling $27.6 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 fourth quarter of 2017 . 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 September 30, 2017 , December 31, 2016 , and September 30, 2016 , auction guarantee advances outstanding totaled $1.1 million , $1 million , and $2.3 million respectively. As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , the estimated fair value of our obligation to perform under our outstanding auction guarantees totaled $5 million , $0.6 million , and $6.2 million , respectively, and is recorded within Accounts Payable and Accrued Liabilities on our Condensed Consolidated Balance Sheets. As of November 2, 2017 , we had outstanding auction guarantees totaling $246.8 million and, as of that date, our financial exposure was reduced by irrevocable bids totaling $109.4 million . Each of the auction guarantees outstanding as of November 2, 2017 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 fourth quarter of 2017 . As of November 2, 2017 , we have advanced $11.3 million of the total guaranteed amount.

Share-Based Payments

Share-Based Payments	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-Based Payments	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 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 three and nine months ended September 30, 2017 and 2016 , compensation expense for share-based payments made to employees was reflected in the following accounts in our Condensed Consolidated Statements of Operations (in thousands of dollars): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Salaries and related costs $ 5,408 $ 2,743 $ 17,423 $ 10,871 Voluntary separation incentive programs — (183 ) — (823 ) Total share-based payment expense (pre-tax) $ 5,408 $ 2,560 $ 17,423 $ 10,048 Total share-based payment expense (after-tax) $ 3,657 $ 1,984 $ 11,654 $ 7,394 For the three and nine months ended September 30, 2016 , our Condensed Consolidated Statements of Operations include credits of ($0.2) million and ($0.8) million , respectively, related to the voluntary separation incentive programs enacted in the fourth quarter of 2015. These credits were the result of changes in our estimate of the number of performance-based stock units held by program participants that were expected to vest. 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. For the nine months ended September 30, 2017 , we recognized a $2.6 million excess tax benefit related to share-based payments in our Condensed Consolidated Statements of Operations. This tax benefit represents the amount by which the tax deduction resulting from the vesting of share-based payments in the period exceeded the tax benefit initially recognized in our Condensed Consolidated Financial Statements. For the nine months ended September 30, 2016 , we recognized a ($1.3) million tax shortfall related to share-based payments. This tax shortfall represents the amount by which the tax deduction resulting from the vesting of share-based payments in the period was less than the tax benefit initially recognized in our Condensed 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 Condensed Consolidated Balance Sheets. As of September 30, 2017 , unrecognized compensation expense related to the unvested portion of share-based payments to employees was $27.5 million . This compensation expense is expected to be amortized over a weighted-average period of approximately 2.2 years. We do not capitalize any 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 -year service 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. For the nine months ended September 30, 2017 , the Compensation Committee approved share-based payment awards with a total grant date fair value of $31 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 units awarded 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 . • 404,785 RSU's with a grant date fair value of $16.4 million and annual vesting opportunities over a three -year service period. Summary of Outstanding Share-Based Payment Awards —For the nine months ended September 30, 2017 , changes to the number of outstanding RSU’s, PSU’s, and restricted shares were as follows (shares in thousands) Restricted Shares, RSU's and PSU's Weighted Average Grant Date Fair Value Outstanding at January 1, 2017 2,235 $ 36.40 Granted 775 $ 39.92 Vested (834 ) $ 39.25 Canceled (186 ) $ 38.77 Outstanding at September 30, 2017 1,990 $ 34.95 As of September 30, 2017 , 2.3 million shares were available for future awards issued pursuant to the Restricted Stock Unit Plan. The aggregate fair value of RSU’s and PSU's that vested during the nine months ended September 30, 2017 and 2016 was $39.5 million and $15 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 are exercisable into authorized, but unissued shares of our common stock. Stock options vest evenly over four years and expire ten years after the date of grant. As of September 30, 2017 , 104,100 shares of our common stock were available for the issuance of stock options under the Stock Option Plan. As of September 30, 2017 , 50,000 stock options were outstanding and exercisable with a weighted average exercise price of $22.11 per share, a weighted average remaining contractual term of 2.4 years, and an aggregate intrinsic value of $1.2 million . No stock options were exercised or granted during the nine months ended September 30, 2017 and 2016 . 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 the common stock on the New York Stock Exchange 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. For the three and nine months ended September 30, 2017 and 2016 , we recognized $0.3 million and $0.8 million , respectively, within General and Administrative Expenses in our Condensed Consolidated Statements of Operations related to common stock shares awarded under the Directors Stock Plan. As of September 30, 2017 , 164,089 deferred stock units were outstanding under the Directors Stock Plan and 120,337 units were available for future issuance.

(Loss) Earnings Per Share

(Loss) Earnings Per Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
(Loss) Earnings Per Share	Earnings Per Share Basic (loss) earnings per share —Basic (loss) 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 shares held by employees, both of which have non-forfeitable rights to dividends (see Note 17). Diluted (loss) earnings per share —Diluted (loss) earnings per share attributable to Sotheby's common shareholders is computed in a similar manner to basic (loss) 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 17 ). For the three and nine months ended September 30, 2017 and 2016, 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 (loss) earnings per share for the three and nine months ended September 30, 2017 and 2016 (in thousands, except per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Basic: Numerator: Net (loss) income attributable to Sotheby’s $ (23,479 ) $ (54,470 ) $ 42,087 $ 8,610 Less: Net income attributable to participating securities — — 643 115 Net (loss) income attributable to Sotheby’s common shareholders $ (23,479 ) $ (54,470 ) $ 41,444 $ 8,495 Denominator: Weighted average common shares outstanding 52,532 55,013 52,755 58,379 Basic (loss) earnings per share - Sotheby’s common shareholders $ (0.45 ) $ (0.99 ) $ 0.79 $ 0.15 Diluted : Numerator: Net (loss) income attributable to Sotheby’s $ (23,479 ) $ (54,470 ) $ 42,087 $ 8,610 Less: Net income attributable to participating securities — — 643 115 Net (loss) income attributable to Sotheby’s common shareholders $ (23,479 ) $ (54,470 ) $ 41,444 $ 8,495 Denominator: Weighted average common shares outstanding 52,532 55,013 52,755 58,379 Weighted average effect of dilutive potential common shares: Performance share units — — 243 433 Deferred stock units — — 159 150 Stock options — — 26 13 Weighted average dilutive potential common shares outstanding — — 428 596 Weighted average diluted shares outstanding 52,532 55,013 53,183 58,975 Diluted (loss) earnings per share - Sotheby’s common shareholders $ (0.45 ) $ (0.99 ) $ 0.78 $ 0.14 The decrease in weighted average common shares outstanding between the current and prior year is due to common stock repurchases made throughout 2016 and in the second and third quarters of 2017. See Note 12 for additional information on our share repurchase program.

Acquisition of Art Agency, Part

Acquisition of Art Agency, Partners	9 Months Ended
	Sep. 30, 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 Condensed Consolidated Statements of Operations. For the three and nine months ended September 30, 2016 , we recognized $17.2 million and $21.6 million , respectively, of compensation expense associated with the AAP earn-out arrangement based on our estimate of progress against the Target. 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 Condensed Consolidated Balance Sheets, and the remaining liability ( $17.5 million ) is recorded within Other Long-Term Liabilities. See Note 10 . 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 (see Note 5) 34,490 Intangible assets - customer relationships (see Note 5) 10,800 Intangible assets - non-compete agreements (see Note 5) 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 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.

Related Party Transactions

Related Party Transactions	9 Months Ended
	Sep. 30, 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 the Board of Directors and management, buy and sell property at our auctions or through private sales brokered by Sotheby's. For the three months ended September 30, 2017, we recognized Agency Commissions and Fees of less than $0.1 million , related to property sold or purchased by related parties. For the nine months ended September 30, 2017, we recognized Agency Commissions and Fees of $4.7 million , related to property sold or purchased by related parties. For the three and nine months ended September 30, 2016 , such amounts totaled $0.1 million and $0.7 million , respectively. As of September 30, 2017 , December 31, 2016, and September 30, 2016, amounts owed to related party consignors totaled $0.4 million , $3.6 million , and $0.9 million , respectively. As of September 30, 2017 and December 31, 2016, Accounts Receivable (net) included $0.1 million and $1.8 million , respectively, associated with auction purchases made by related parties.

Recent Accounting Standards Not

Recent Accounting Standards Not Yet Adopted	9 Months Ended
	Sep. 30, 2017
Accounting Changes and Error Corrections [Abstract]
Recent Accounting Standards Not Yet Adopted	Recent Accounting Standards Not Yet Adopted 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. We have identified all material contract types and have substantially completed our assessment of the impact of adopting ASU 2014-09. Based on our assessment to date, the adoption of ASU 2014-09 will not have a material impact on the timing of our revenue recognition. However, there will be a change in the presentation of certain revenues and expenses currently recorded on a net basis in our statement of operations. In particular, certain auction commissions and fees shared with irrevocable bid counterparties and third parties who introduce us to consignors, which are currently reported as a reduction of Agency Commissions and Fees, will be reported as a component of Agency Direct Costs. Similarly, various agency-related expense recoveries (most notably, recoveries related to the shipment of property) that are currently reported as a reduction of Agency Direct Costs, will be reported as a component of Agency Commissions and Fees. We will disclose the quantitative impact of adopting ASU 2014-09 in our Form 10-K for the year ending December 31, 2017. In addition, we are in the process of identifying and implementing changes to our business processes, systems and controls to support the adoption of this standard. 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. We are currently assessing the potential impact of adopting ASU 2016-01 on our financial statements. 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. We are currently assessing the potential impact of adopting ASU 2016-02 on our financial statements. 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. 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. 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. We do not expect the adoption of ASU 2017-01 to have a material impact on our financial statements. 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. 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 6. 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. 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.

Segment Reporting (Tables)

Segment Reporting (Tables)	9 Months Ended
	Sep. 30, 2017
Segment Reporting [Abstract]
Schedule of Segment Information	The following table presents our segment information for the three and nine months ended September 30, 2017 and 2016 (in thousands of dollars): Three Months Ended September 30, 2017 Agency SFS All Other Reconciling items (a) Total Revenues $ 152,160 $ 13,781 $ 7,537 $ (2,084 ) $ 171,394 Segment (loss) income before taxes $ (55,061 ) $ 5,965 $ 4,282 $ (901 ) (b) $ (45,715 ) Three Months Ended September 30, 2016 Revenues $ 74,095 $ 13,150 $ 6,259 $ (2,012 ) $ 91,492 Segment (loss) income before taxes $ (77,455 ) $ 7,087 $ (1,907 ) $ (1,220 ) (b) $ (73,495 ) Nine Months Ended September 30, 2017 Revenues $ 615,092 $ 44,514 $ 20,914 $ (6,691 ) $ 673,829 Segment income before taxes $ 13,743 $ 22,177 $ 9,003 $ (2,034 ) (b) $ 42,889 Nine Months Ended September 30, 2016 Revenues $ 436,928 $ 46,182 $ 19,117 $ (5,539 ) $ 496,688 Segment (loss) income before taxes $ (17,031 ) $ 28,027 $ 1,318 $ (1,807 ) (b) $ 10,507 (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 (loss) income before taxes are detailed in the table below.
Reconciliation of Segment (Loss) Income Before Taxes	The table below presents a reconciliation of segment (loss) income before taxes to consolidated (loss) income before taxes for the three and nine months ended September 30, 2017 and 2016 (in thousands of dollars): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Agency $ (55,061 ) $ (77,455 ) $ 13,743 $ (17,031 ) SFS 5,965 7,087 22,177 28,027 All Other 4,282 (1,907 ) 9,003 1,318 Segment (loss) income before taxes (44,814 ) (72,275 ) 44,923 12,314 Reconciling items: Equity in earnings of investees (a) (901 ) (1,220 ) (2,034 ) (1,807 ) (Loss) income before taxes $ (45,715 ) $ (73,495 ) $ 42,889 $ 10,507 (a) For segment reporting purposes, our share of earnings related to equity investees is included as part of (loss) income before taxes. However, such earnings are reported separately below (loss) income before taxes in our Condensed Consolidated Statements of Operations.
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 September 30, 2017 , December 31, 2016 , and September 30, 2016 (in thousands of dollars): September 30, 2017 December 31, 2016 September 30, 2016 Agency $ 1,441,249 $ 1,759,670 $ 1,608,803 SFS 627,815 687,649 683,331 All Other 39,431 42,246 40,903 Total segment assets 2,108,495 2,489,565 2,333,037 Unallocated amounts and reconciling items: Deferred tax assets and income tax receivable 38,180 14,861 24,644 Consolidated assets $ 2,146,675 $ 2,504,426 $ 2,357,681

Receivables (Tables)

Receivables (Tables)	9 Months Ended
	Sep. 30, 2017
Receivables [Abstract]
Schedule of Aggregate LTV Ratio	The table below provides the aggregate LTV ratio for the SFS loan portfolio as of September 30, 2017 , December 31, 2016 , and September 30, 2016 (in thousands of dollars): September 30, December 31, September 30, Secured loans $ 602,176 $ 675,109 $ 655,152 Low auction estimate of collateral $ 1,378,737 $ 1,405,856 $ 1,347,334 Aggregate LTV ratio 44 % 48 % 49 % The table below provides the aggregate LTV ratio for secured loans made by SFS with an LTV ratio above 50% as of September 30, 2017 , December 31, 2016 , and September 30, 2016 (in thousands of dollars): September 30, December 31, September 30, Secured loans with an LTV ratio above 50% $ 179,568 $ 270,111 $ 354,698 Low auction estimate of collateral related to secured loans with an LTV ratio above 50% $ 306,603 $ 486,973 $ 646,259 Aggregate LTV ratio of secured loans with an LTV ratio above 50% 59 % 55 % 55 %
Schedule of Other Credit Quality Information	The table below provides other credit quality information regarding secured loans made by SFS as of September 30, 2017 , December 31, 2016 , and September 30, 2016 (in thousands of dollars): September 30, December 31, September 30, Total secured loans $ 602,176 $ 675,109 $ 655,152 Loans past due $ 79,038 $ 90,508 $ 17,204 Loans more than 90 days past due $ 78,367 $ 158 $ 926 Non-accrual loans $ — $ 158 $ 167 Impaired loans $ — $ — $ — Allowance for credit losses: Allowance for credit losses for impaired loans $ — $ — $ — Allowance for credit losses based on historical data 1,295 1,270 1,302 Total allowance for credit losses - secured loans $ 1,295 $ 1,270 $ 1,302
Schedule of Activity Related to Allowance for Credit Losses	During the period January 1, 2017 to September 30, 2017 , activity related to the Allowance for Credit Losses was as follows (in thousands of dollars): Allowance for credit losses as of January 1, 2017 $ 1,270 Change in loan loss provision 25 Allowance for credit losses as of September 30, 2017 $ 1,295

Goodwill and Intangible Assets

Goodwill and Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Schedule of Goodwill	For the nine months ended September 30, 2017 and 2016 , changes in the carrying value of Goodwill were as follows (in thousands of dollars): Nine Months Ended September 30, 2017 Nine Months Ended September 30, 2016 Agency All Other Total Agency All Other Total Beginning balance as of December 31 $ 43,878 $ 6,151 $ 50,029 $ 13,621 $ — $ 13,621 Goodwill acquired (see Note 19) — — — 28,339 6,151 34,490 Foreign currency exchange rate changes 467 — 467 (278 ) — (278 ) Ending balance as of September 30 $ 44,345 $ 6,151 $ 50,496 $ 41,682 $ 6,151 $ 47,833
Schedule of Indefinite-Lived Intangible Assets	As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , intangible assets consisted of the following (in thousands of dollars): Amortization Period September 30, 2017 December 31, 2016 September 30, Indefinite lived intangible assets: License (a) N/A $ 324 $ 324 $ 324 Intangible assets subject to amortization: Customer relationships - AAP (see Note 19) 8 years 10,800 10,800 10,800 Non-compete agreements - AAP (see Note 19) 6 years 3,060 3,060 3,060 Artworks database (b) 10 years 1,200 1,125 1,125 Total intangible assets subject to amortization 15,060 14,985 14,985 Accumulated amortization (3,397 ) (1,916 ) (1,395 ) Total amortizable intangible assets (net) 11,663 13,069 13,590 Total intangible assets (net) $ 11,987 $ 13,393 $ 13,914 (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 along 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	As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , intangible assets consisted of the following (in thousands of dollars): Amortization Period September 30, 2017 December 31, 2016 September 30, Indefinite lived intangible assets: License (a) N/A $ 324 $ 324 $ 324 Intangible assets subject to amortization: Customer relationships - AAP (see Note 19) 8 years 10,800 10,800 10,800 Non-compete agreements - AAP (see Note 19) 6 years 3,060 3,060 3,060 Artworks database (b) 10 years 1,200 1,125 1,125 Total intangible assets subject to amortization 15,060 14,985 14,985 Accumulated amortization (3,397 ) (1,916 ) (1,395 ) Total amortizable intangible assets (net) 11,663 13,069 13,590 Total intangible assets (net) $ 11,987 $ 13,393 $ 13,914 (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 along 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 Estimated Aggregate 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 September 30, 2017 balance sheet date are as follows (in thousands of dollars): Period Amount October 2017 to September 2018 $ 1,981 October 2018 to September 2019 $ 1,981 October 2019 to September 2020 $ 1,981 October 2020 to September 2021 $ 1,981 October 2021 to September 2022 $ 1,598

Defined Benefit Pension Plan (T

Defined Benefit Pension Plan (Tables)	9 Months Ended
	Sep. 30, 2017
Retirement Benefits [Abstract]
Components of Net Credits Related to the U.K. Pension Plan	For the three and nine months ended September 30, 2017 and 2016 , the components of the net credits related to the U.K. Pension Plan were as follows (in thousands of dollars): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Service cost $ — $ — $ — $ 1,153 Interest cost 2,047 2,385 5,984 7,600 Expected return on plan assets (3,598 ) (4,324 ) (10,519 ) (13,778 ) Prior service cost 15 — 45 — Amortization of actuarial loss 289 — 842 — Amortization of prior service cost (25 ) — (71 ) — Net pension credit $ (1,272 ) $ (1,939 ) $ (3,719 ) $ (5,025 )

Debt (Tables)

Debt (Tables)	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Summary of Information Related to the Credit Agreement	The following tables summarize information related to the Credit Agreement as of and for the periods ended September 30, 2017 , December 31, 2016 , and September 30, 2016 (in thousands of dollars): As of and for the three and nine months ended September 30, 2017 Agency Credit Facility SFS Credit Facility Total Maximum borrowing capacity (a) $ 300,000 $ 1,035,000 (a) $ 1,335,000 (a) Borrowing base $ 134,936 $ 503,132 $ 638,068 Borrowings outstanding $ — $ 434,000 $ 434,000 Available borrowing capacity (a) (b) $ 134,936 $ 69,132 $ 204,068 Average Borrowings Outstanding: Three months ended September 30, 2017 $ — $ 508,342 $ 508,342 Nine months ended September 30, 2017 $ — $ 537,374 $ 537,374 Borrowing Costs - Three Months Ended September 30, 2017: Interest $ — (c) $ 4,746 (d) $ 4,746 Fees 777 (c) 1,308 (d) 2,085 Total $ 777 $ 6,054 $ 6,831 Borrowing Costs - Nine Months Ended September 30, 2017: Interest $ — (c) $ 13,471 (d) $ 13,471 Fees 2,141 (c) 2,698 (d) 4,839 Total $ 2,141 $ 16,169 $ 18,310 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 (b) $ 165,443 $ 4,021 $ 169,464 Average borrowings outstanding $ — $ 534,433 $ 534,433 As of and for the three and nine months ended September 30, 2016 Agency Credit Facility SFS Credit Facility Total Maximum borrowing capacity $ 300,000 $ 1,035,000 $ 1,335,000 Borrowing base $ 174,548 $ 554,969 $ 729,517 Borrowings outstanding $ — $ 553,000 $ 553,000 Available borrowing capacity (b) $ 174,548 $ 1,969 $ 176,517 Average Borrowings Outstanding: Three months ended September 30, 2016 $ — $ 523,397 $ 523,397 Nine months ended September 30, 2016 $ — $ 527,204 $ 527,204 Borrowing Costs - Three Months Ended September 30, 2016: Interest $ — (c) $ 3,694 (d) $ 3,694 Fees 640 (c) 739 (d) 1,379 Total $ 640 $ 4,433 $ 5,073 Borrowing Costs - Nine Months Ended September 30, 2016: Interest $ — (c) $ 10,824 (d) $ 10,824 Fees 2,028 (c) 2,156 (d) 4,184 Total $ 2,028 $ 12,980 $ 15,008 (a) As discussed above, on September 27, 2017, we provided notice to our lenders to reduce the borrowing capacity of the SFS Credit Facility by $235 million , effective October 2, 2017. (b) The available borrowing capacity is calculated as the borrowing base less borrowings outstanding. (c) Borrowing costs related to the Agency Credit Facility, which include interest and fees, are reflected in our Condensed Consolidated Statements of Operations as Interest Expense. (d) Borrowing costs related to the SFS Credit Facility are reflected in our Condensed Consolidated Statements of Operations within Cost of Finance Revenues. For the three and nine months ended September 30, 2017 , the weighted average cost of borrowings related to the SFS Credit Facility was approximately 4.8% and 4.0% , respectively. For the three and nine months ended September 30, 2017 , 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. Excluding this charge, the weighted average cost of borrowings related to the SFS Credit Facility was approximately 4.2% and 3.8% for the three and nine months ended September 30, 2017, respectively. For the three and nine months ended September 30, 2016, the weighted average cost of borrowings related to the SFS Credit Facility was approximately 3.4% and 3.3% , respectively.
Schedule of Long-Term Debt	As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , Long-Term Debt consisted of the following (in thousands of dollars): September 30, December 31, September 30, York Property Mortgage, net of unamortized debt issuance costs of $4,797, $5,555, and $5,808 $ 272,261 $ 309,212 $ 310,834 2022 Senior Notes, net of unamortized debt issuance costs of $3,159, $3,642, and $3,803 296,841 296,358 296,197 Less current portion: York Property Mortgage, net of unamortized debt issuance costs of $1,010, $1,010, and $1,010 (11,912 ) (6,629 ) (6,546 ) Total Long-Term Debt, net $ 557,190 $ 598,941 $ 600,485
Schedule of Aggregate Future Principal and Interest Payments	The aggregate future principal and interest payments due under the Credit Agreement, the York Property Mortgage, and the 2022 Senior Notes during the five-year period after September 30, 2017 are as follows (in thousands of dollars): Period Amount October 2017 to September 2018 $ 38,233 October 2018 to September 2019 $ 37,494 October 2019 to September 2020 $ 471,953 October 2020 to September 2021 $ 38,567 October 2021 to September 2022 $ 244,850

Derivative Financial Instrume33

Derivative Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2017
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Fair Value Information Related to Derivative Financial Instruments	The following tables present fair value information related to the derivative financial instruments that we have designated as hedging instruments as of September 30, 2017 , December 31, 2016 , and September 30, 2016 (in thousands of dollars): Assets Liabilities September 30, 2017 Balance Sheet Classification Fair Value Balance Sheet Classification Fair Value Cash Flow Hedges: Interest rate swap Other Current Assets $ 238 N/A $ — Interest rate collar N/A — Other Current Liabilities 1,375 Interest rate collar N/A — Other Long-Term Liabilities 2,900 Total cash flow hedges 238 — 4,275 Net Investment Hedges: Foreign exchange contracts N/A — Other Current Liabilities 3,626 Total $ 238 $ 7,901 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 Assets Liabilities September 30, 2016 Balance Sheet Classification Fair Value Balance Sheet Classification Fair Value Cash Flow Hedges: Interest rate swap N/A $ — Other Current Liabilities $ 651 Interest rate collar N/A — Other Long-Term Liabilities 14,696 Total cash flow hedges — 15,347 Net Investment Hedges: Foreign exchange contracts Other Current Assets 20,098 Other Current Liabilities — Total $ 20,098 $ 15,347
Summary of the Effect of the Derivative Financial Instruments	The following tables summarize the effect of the derivative financial instruments that we have designated as hedging instruments on our Condensed Consolidated Statements of Operations and Condensed Consolidated Statements of Comprehensive (Loss) Income for the three and nine months ended September 30, 2017 and 2016 (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 (Loss) Income Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Effective Portion Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Ineffective Portion Three Months Ended September 30, 2017 2016 2017 2016 2017 2016 Cash Flow Hedges: Interest rate swaps $ (7 ) $ 223 Interest Expense $ (8 ) $ 192 $ — $ — Interest rate collar 125 925 Interest Expense 300 — — — Total cash flow hedges 118 1,148 292 192 — — Net Investment Hedges: Foreign exchange contracts (911 ) 4,323 N/A — — — — Total $ (793 ) $ 5,471 $ 292 $ 192 $ — $ — 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 Nine Months Ended September 30, 2017 2016 2017 2016 2017 2016 Cash Flow Hedges: Interest rate swaps $ 127 $ (860 ) Interest Expense $ 27 $ 631 $ — $ — Interest rate collar 210 (4,867 ) Interest Expense 300 — — — Interest rate collar — — Non-operating income — — 622 — Total cash flow hedges 337 — (5,727 ) 327 631 622 — Net Investment Hedges: Foreign exchange contracts (2,989 ) 10,096 N/A — — — — Total $ (2,652 ) $ 4,369 $ 327 $ 631 $ 622 $ —

Supplemental Condensed Consol34

Supplemental Condensed Consolidated Balance Sheet Information (Tables)	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Schedule of Prepaid Expenses and Other Current Assets	As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , Prepaid Expenses and Other Current Assets consisted of the following (in thousands of dollars): September 30, December 31, September 30, Prepaid expenses $ 31,623 $ 20,436 $ 29,716 Derivative financial instruments (see Note 8) 239 30,340 20,098 Other (a) 23,661 25,831 16,052 Total Prepaid Expenses and Other Current Assets $ 55,523 $ 76,607 $ 65,866 (a) Other principally includes receivables related to insurance recoveries and, to a much lesser extent, other miscellaneous short-term assets.
Schedule of Other Long-Term Assets	As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , Other Long-Term Assets consisted of the following (in thousands of dollars): September 30, December 31, September 30, Defined benefit pension plan asset (see Note 6) $ 90,559 $ 78,576 $ 63,563 Equity method investments (a) 46,207 43,143 41,695 Trust assets related to deferred compensation liability 25,325 26,713 27,962 Restricted cash (b) 17,835 1,064 1,127 Other 16,156 15,928 16,191 Total Other Long-Term Assets $ 196,082 $ 165,424 $ 150,538 (a) Includes our equity method investments in RM Sotheby's and AMA, as well as a partnership that was formed in the second quarter of 2017 through which artworks are being purchased and sold. As of September 30, 2017, our investment in this partnership was $5.4 million , representing our 50% ownership interest. (b) As of September 30, 2017, restricted cash reflected within Other Long-Term Assets principally relates to $15.3 million of funds held in escrow pending the final settlement of a sale. As of December 31, 2016 and September 30, 2016, restricted cash reflected within Other Long-Term Assets primarily consists of segregated cash related to long-term lease arrangements.
Schedule of Other Long-Term Liabilities	As of September 30, 2017 , December 31, 2016 , and September 30, 2016 , Other Long-Term Liabilities consisted of the following (in thousands of dollars): September 30, December 31, September 30, Deferred compensation liability $ 24,563 $ 25,914 $ 26,086 Acquisition earn-out consideration (see Note 19) 17,500 26,250 — Interest rate collar liability (see Note 8) 2,900 5,952 14,696 Other 6,704 6,964 7,010 Total Other Long-Term Liabilities $ 51,667 $ 65,080 $ 47,792

Supplemental Condensed Consol35

Supplemental Condensed Consolidated Cash Flow Information (Tables)	9 Months Ended
	Sep. 30, 2017
Supplemental Cash Flow Information [Abstract]
Supplemental Condensed Consolidated Cash Flow Information	For the nine months ended September 30, 2017 and 2016 , changes in other operating assets and liabilities as reported in the Condensed Consolidated Statements of Cash Flows included the following (in thousands of dollars): Nine Months Ended September 30, 2017 2016 (Increase) decrease in: Prepaid expenses and other current assets $ (2,443 ) $ (7,974 ) Other long-term assets 788 10,748 Income tax receivables and deferred income tax assets (34,168 ) 11,835 Decrease in: Accrued income taxes and deferred income tax liabilities (15,156 ) (20,220 ) Accounts payable and accrued liabilities and other liabilities (64,697 ) (11,841 ) Total changes in other operating assets and liabilities $ (115,676 ) $ (17,452 )

Shareholders' Equity and Divi36

Shareholders' Equity and Dividends (Tables)	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Schedule of Information Regarding Common Stock Repurchase Program	The following table provides information regarding our common stock repurchase program for the nine months ended September 30, 2017 and 2016 (in thousands, except for per share data): Nine Months Ended September 30, 2017 September 30, 2016 Shares repurchased 866 11,093 Aggregate purchase price $ 40,193 $ 286,084 Average price per share $ 46.40 $ 25.79

Accumulated Other Comprehensi37

Accumulated Other Comprehensive Loss (Tables)	9 Months Ended
	Sep. 30, 2017
Equity [Abstract]
Summary of Changes in Accumulated Other Comprehensive Loss	The following is a summary of the changes in Accumulated Other Comprehensive Loss for the three and nine months ended September 30, 2017 and 2016 (in thousands of dollars): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Currency Translation Adjustments Balance at beginning of period $ (80,327 ) $ (71,274 ) $ (89,478 ) $ (52,279 ) Other comprehensive income (loss) before reclassifications, net of tax of $851, ($4,946), $2,272, and ($7,691) 3,870 (4,895 ) 13,021 (23,890 ) Other comprehensive income (loss) 3,870 (4,895 ) 13,021 (23,890 ) Balance at end of period (76,457 ) (76,169 ) (76,457 ) (76,169 ) Cash Flow Hedges Balance at beginning of period (2,788 ) (10,742 ) (3,664 ) (4,306 ) Other comprehensive income (loss) before reclassifications, net of tax of $72, $710 , $207, and ( $3,550) 118 1,148 337 (5,727 ) Reclassifications from accumulated other comprehensive loss, net of tax of $181 , $119, $588, and $391 292 192 949 631 Other comprehensive income (loss) 410 1,340 1,286 (5,096 ) Balance at end of period (2,378 ) (9,402 ) (2,378 ) (9,402 ) Net Investment Hedges Balance at beginning of period 14,540 5,773 16,618 — Other comprehensive (loss) income before reclassifications, net of tax of ($552), $2,817, ($1,822), and $6,694 (911 ) 4,323 (2,989 ) 10,096 Other comprehensive (loss) income (911 ) 4,323 (2,989 ) 10,096 Balance at end of period 13,629 10,096 13,629 10,096 Defined Benefit Pension Plan Balance at beginning of period (14,211 ) (8,629 ) (13,834 ) (9,619 ) Currency translation adjustments (433 ) 354 (1,233 ) 1,263 Net actuarial gain, net of tax of $0, $0, $0, and ($81) — — — 81 Prior service cost amortization, net of tax of ($5), $0, ($12), and $0 (20 ) — (59 ) — Actuarial loss amortization, net of tax of $50, $0, $141, and $0 239 — 701 — Other comprehensive (loss) income (214 ) 354 (591 ) 1,344 Balance at end of period (14,425 ) (8,275 ) (14,425 ) (8,275 ) Total other comprehensive income (loss) attributable to Sotheby's 3,155 1,122 10,727 (17,546 ) Accumulated other comprehensive loss as of September 30 $ (79,631 ) $ (83,750 ) $ (79,631 ) $ (83,750 )
Summary of Reclassification Adjustments	The following is a summary of the reclassification adjustments made to Accumulated Other Comprehensive Loss for the three and nine months ended September 30, 2017 and 2016 (in thousands of dollars): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Cash Flow Hedges Settlements $ 473 $ 311 $ 1,537 $ 1,022 Tax effect (181 ) (119 ) (588 ) (391 ) Reclassification adjustments, net of tax 292 192 949 631 Defined Benefit Pension Plan Prior service cost amortization (25 ) — (71 ) — Actuarial loss amortization 289 — 842 — Pre-tax total 264 — 771 — Tax effect (45 ) — (129 ) — Reclassification adjustments, net of tax 219 — 642 — Total reclassification adjustments, net of tax $ 511 $ 192 $ 1,591 $ 631

Share-Based Payments (Tables)

Share-Based Payments (Tables)	9 Months Ended
	Sep. 30, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Compensation Expense for Share-Based Payments	For the three and nine months ended September 30, 2017 and 2016 , compensation expense for share-based payments made to employees was reflected in the following accounts in our Condensed Consolidated Statements of Operations (in thousands of dollars): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Salaries and related costs $ 5,408 $ 2,743 $ 17,423 $ 10,871 Voluntary separation incentive programs — (183 ) — (823 ) Total share-based payment expense (pre-tax) $ 5,408 $ 2,560 $ 17,423 $ 10,048 Total share-based payment expense (after-tax) $ 3,657 $ 1,984 $ 11,654 $ 7,394
Schedule of Changes to the Number of Outstanding RSU's, PSU's, and Restricted Shares	For the nine months ended September 30, 2017 , changes to the number of outstanding RSU’s, PSU’s, and restricted shares were as follows (shares in thousands) Restricted Shares, RSU's and PSU's Weighted Average Grant Date Fair Value Outstanding at January 1, 2017 2,235 $ 36.40 Granted 775 $ 39.92 Vested (834 ) $ 39.25 Canceled (186 ) $ 38.77 Outstanding at September 30, 2017 1,990 $ 34.95

(Loss) Earnings Per Share (Tabl

(Loss) Earnings Per Share (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Computation Of Basic And Diluted (Loss) Earnings Per Share	The table below summarizes the computation of basic and diluted (loss) earnings per share for the three and nine months ended September 30, 2017 and 2016 (in thousands, except per share amounts): Three Months Ended September 30, Nine Months Ended September 30, 2017 2016 2017 2016 Basic: Numerator: Net (loss) income attributable to Sotheby’s $ (23,479 ) $ (54,470 ) $ 42,087 $ 8,610 Less: Net income attributable to participating securities — — 643 115 Net (loss) income attributable to Sotheby’s common shareholders $ (23,479 ) $ (54,470 ) $ 41,444 $ 8,495 Denominator: Weighted average common shares outstanding 52,532 55,013 52,755 58,379 Basic (loss) earnings per share - Sotheby’s common shareholders $ (0.45 ) $ (0.99 ) $ 0.79 $ 0.15 Diluted : Numerator: Net (loss) income attributable to Sotheby’s $ (23,479 ) $ (54,470 ) $ 42,087 $ 8,610 Less: Net income attributable to participating securities — — 643 115 Net (loss) income attributable to Sotheby’s common shareholders $ (23,479 ) $ (54,470 ) $ 41,444 $ 8,495 Denominator: Weighted average common shares outstanding 52,532 55,013 52,755 58,379 Weighted average effect of dilutive potential common shares: Performance share units — — 243 433 Deferred stock units — — 159 150 Stock options — — 26 13 Weighted average dilutive potential common shares outstanding — — 428 596 Weighted average diluted shares outstanding 52,532 55,013 53,183 58,975 Diluted (loss) earnings per share - Sotheby’s common shareholders $ (0.45 ) $ (0.99 ) $ 0.78 $ 0.14

Acquisition of Art Agency, Pa40

Acquisition of Art Agency, Partners (Tables)	9 Months Ended
	Sep. 30, 2017
Business Combinations [Abstract]
Summary of the Allocation of the Total Purchase Price Paid for AAP	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 (see Note 5) 34,490 Intangible assets - customer relationships (see Note 5) 10,800 Intangible assets - non-compete agreements (see Note 5) 3,060 Deferred tax assets 1,094 Total purchase price $ 51,189

Basis of Presentation (Details)

Basis of Presentation (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Ownership interest in joint venture (as a percent)	80.00%
Ownership interest reported as Noncontrolling Interest (as a percent)	20.00%
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Discrete income tax benefit recorded	$ 2,600
Classification of excess tax benefits within Operating Activities	(73,639)	$ (99,850)
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Discrete income tax benefit recorded	$ 2,600
Decrease to effective income tax rate	6.00%
Classification of excess tax benefits within Operating Activities	$ 2,600

Seasonality of Business (Detail

Seasonality of Business (Details) - principal_selling_season	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Sep. 30, 2017
Seasonality Of Business [Abstract]
Number of principal selling seasons			2
Second and fourth quarter Net Auction Sales (as a percent)	82.00%	78.00%
Auction commission revenues (as a percent)	75.00%	75.00%

Segment Reporting - Narrative (

Segment Reporting - Narrative (Details)	9 Months Ended
	Sep. 30, 2017segment
Segment Reporting [Abstract]
Number of operating segments	2

Segment Reporting - Schedule of

Segment Reporting - Schedule of Segment Information (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting [Line Items]
Revenues	$ 171,394	$ 91,492	$ 673,829	$ 496,688
Segment (loss) income before taxes	(45,715)	(73,495)	42,889	10,507
Operating Segments
Segment Reporting [Line Items]
Segment (loss) income before taxes	(44,814)	(72,275)	44,923	12,314
Operating Segments | Agency
Segment Reporting [Line Items]
Revenues	152,160	74,095	615,092	436,928
Segment (loss) income before taxes	(55,061)	(77,455)	13,743	(17,031)
Operating Segments | SFS
Segment Reporting [Line Items]
Revenues	13,781	13,150	44,514	46,182
Segment (loss) income before taxes	5,965	7,087	22,177	28,027
Operating Segments | All Other
Segment Reporting [Line Items]
Revenues	7,537	6,259	20,914	19,117
Segment (loss) income before taxes	4,282	(1,907)	9,003	1,318
Reconciling items
Segment Reporting [Line Items]
Revenues	(2,084)	(2,012)	(6,691)	(5,539)
Segment (loss) income before taxes	$ (901)	$ (1,220)	$ (2,034)	$ (1,807)

Segment Reporting - Reconciliat

Segment Reporting - Reconciliation of Segment (Loss) Income Before Taxes (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment (loss) income before taxes	$ (45,715)	$ (73,495)	$ 42,889	$ 10,507
Equity in earnings of investees	901	1,220	2,034	1,807
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment (loss) income before taxes	(44,814)	(72,275)	44,923	12,314
Operating Segments | Agency
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment (loss) income before taxes	(55,061)	(77,455)	13,743	(17,031)
Operating Segments | SFS
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment (loss) income before taxes	5,965	7,087	22,177	28,027
Operating Segments | All Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment (loss) income before taxes	4,282	(1,907)	9,003	1,318
Reconciling items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Segment (loss) income before taxes	(901)	(1,220)	(2,034)	(1,807)
Equity in earnings of investees	$ (901)	$ (1,220)	$ (2,034)	$ (1,807)

Segment Reporting - Reconcili46

Segment Reporting - Reconciliation of Segment Assets to Consolidated Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Segment Reporting [Line Items]
Consolidated assets	$ 2,146,675	$ 2,504,426	$ 2,357,681
Operating Segments
Segment Reporting [Line Items]
Consolidated assets	2,108,495	2,489,565	2,333,037
Operating Segments | Agency
Segment Reporting [Line Items]
Consolidated assets	1,441,249	1,759,670	1,608,803
Operating Segments | SFS
Segment Reporting [Line Items]
Consolidated assets	627,815	687,649	683,331
Operating Segments | All Other
Segment Reporting [Line Items]
Consolidated assets	39,431	42,246	40,903
Unallocated amounts and reconciling items
Segment Reporting [Line Items]
Consolidated assets	$ 38,180	$ 14,861	$ 24,644

Receivables - Narrative (Detail

Receivables - Narrative (Details) - USD ($)	3 Months Ended	9 Months Ended
	Jun. 30, 2013	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Accounts, Notes, Loans and Financing Receivable [Line Items]
Period after sale when purchase price is due		30 days
Period from sale date when net proceeds are due		35 days
Accounts Receivable (net)		$ 453,906,000	$ 441,457,000	$ 433,614,000
Period in advance during which sellers may receive funds upon consignment (up to)		1 year
Repayments collected		$ 37,300,000	$ 30,100,000
Target LTV ratio		50.00%	50.00%	50.00%
Permitted borrowings on the portion of any loan that does not exceed a 60% LTV ratio (as a percent)		85.00%
Collateral sales		$ 12,000,000
Unfunded commitments to extend additional credit through SFS		52,400,000
Upfront cash payment		$ 2,125,000	$ 250,000
Minimum
Accounts, Notes, Loans and Financing Receivable [Line Items]
LTV ratio		51.00%
Maximum
Accounts, Notes, Loans and Financing Receivable [Line Items]
LTV ratio		60.00%
Consignor paid before payment was collected from the buyer
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable (net)		$ 144,900,000	138,000,000	$ 90,100,000
Buyer allowed to take possession before making payment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Accounts Receivable (net)		$ 16,400,000	13,000,000	76,300,000
Term loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Initial maturities of term loans (up to) (term)		2 years
Past due loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Target LTV ratio		43.00%
Collateral held against amounts reclassified from Accounts Receivable (net)		$ 183,400,000
Agency
Accounts, Notes, Loans and Financing Receivable [Line Items]
Notes Receivable within the Agency segment		2,700,000	10,200,000	7,500,000
Net Notes Receivable balance of SFS		3,800,000	4,100,000	3,800,000
Repayments collected		5,000,000	13,700,000
Collateral held against amounts reclassified from Accounts Receivable (net)		3,100,000	4,400,000	3,100,000
Auction guarantee advances outstanding		1,100,000	2,300,000	1,000,000
Agency | No longer accruing interest
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of loan		2,100,000
SFS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Net Notes Receivable balance of SFS		602,176,000	655,152,000	675,109,000
Term loans issued by SFS		57,900,000	90,400,000	$ 88,700,000
Loans issued to refinance client auction and private sale purchases		$ 6,500,000	$ 11,700,000
Target LTV ratio		44.00%	49.00%	48.00%
Net Notes Receivable balance past due		$ 79,038,000	$ 17,204,000	$ 90,508,000
Net Notes Receivable balance 90 days past due		78,367,000	926,000	158,000
Collateral held against amounts reclassified from Accounts Receivable (net)		1,378,737,000	1,347,334,000	1,405,856,000
Non-accrual loan outstanding		0	167,000	158,000
Impaired loans outstanding		$ 0	0	0
All Other
Accounts, Notes, Loans and Financing Receivable [Line Items]
Carrying value of loan			$ 2,200,000	$ 2,100,000
Proceeds from sale of equity method investee	$ 4,300,000
All Other | Up-front cash payment
Accounts, Notes, Loans and Financing Receivable [Line Items]
Upfront cash payment	800,000
All Other | Unsecured loans
Accounts, Notes, Loans and Financing Receivable [Line Items]
Proceeds from sale of equity method investee	$ 3,500,000

Receivables - Schedule of Aggre

Receivables - Schedule of Aggregate LTV Ratio (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Segment Reporting [Line Items]
Aggregate LTV ratio	50.00%	50.00%	50.00%
SFS
Segment Reporting [Line Items]
Secured loans	$ 602,176	$ 675,109	$ 655,152
Low auction estimate of collateral	$ 1,378,737	$ 1,405,856	$ 1,347,334
Aggregate LTV ratio	44.00%	48.00%	49.00%
SFS | Loan to Value Ratio Above 50%
Segment Reporting [Line Items]
Secured loans	$ 179,568	$ 270,111	$ 354,698
Low auction estimate of collateral	$ 306,603	$ 486,973	$ 646,259
Aggregate LTV ratio	59.00%	55.00%	55.00%

Receivables - Schedule of Other

Receivables - Schedule of Other Credit Quality Information (Details) - USD ($)	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Allowance for credit losses:
Total allowance for credit losses - secured loans	$ 1,295,000	$ 1,270,000
SFS
Accounts, Notes, Loans and Financing Receivable [Line Items]
Total secured loans	602,176,000	675,109,000	$ 655,152,000
Loans past due	79,038,000	90,508,000	17,204,000
Loans more than 90 days past due	78,367,000	158,000	926,000
Non-accrual loans	0	158,000	167,000
Impaired loans	0	0	0
Allowance for credit losses:
Allowance for credit losses for impaired loans	0	0	0
Allowance for credit losses based on historical data	1,295,000	1,270,000	1,302,000
Total allowance for credit losses - secured loans	$ 1,295,000	$ 1,270,000	$ 1,302,000

Receivables - Schedule of Activ

Receivables - Schedule of Activity Related to Allowance for Credit Losses (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2017USD ($)
Allowance for Loan and Lease Losses
Allowance for credit losses, beginning balance	$ 1,270
Change in loan loss provision	25
Allowance for credit losses, ending balance	$ 1,295

Goodwill and Intangible Asset51

Goodwill and Intangible Assets - Schedule of Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Jun. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Goodwill
Beginning balance		$ 50,029	$ 13,621
Goodwill acquired (see Note 19)		0	34,490
Foreign currency exchange rate changes		467	(278)
Ending balance		50,496	47,833
Agency
Goodwill
Beginning balance		43,878	13,621
Goodwill acquired (see Note 19)	$ 28,300	0	28,339
Foreign currency exchange rate changes		467	(278)
Ending balance		44,345	41,682
All Other
Goodwill
Beginning balance		6,151	0
Goodwill acquired (see Note 19)	$ 6,200	0	6,151
Foreign currency exchange rate changes		0	0
Ending balance		$ 6,151	$ 6,151

Goodwill and Intangible Asset52

Goodwill and Intangible Assets - Schedule of Indefinite and Finite-Lived Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Finite-Lived Intangible Assets [Line Items]
Intangible assets subject to amortization	$ 15,060	$ 14,985	$ 14,985
Accumulated amortization	(3,397)	(1,916)	(1,395)
Total amortizable intangible assets (net)	11,663	13,069	13,590
Total intangible assets (net)	11,987	13,393	13,914
License
Indefinite-lived Intangible Assets [Line Items]
Indefinite-lived intangible assets	$ 324	324	324
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Amortization Period	8 years
Intangible assets subject to amortization	$ 10,800	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	3,060
Artworks database
Finite-Lived Intangible Assets [Line Items]
Amortization Period	10 years
Intangible assets subject to amortization	$ 1,200	$ 1,125	$ 1,125

Goodwill and Intangible Asset53

Goodwill and Intangible Assets - Narrative (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense related to intangible assets	$ 0.5	$ 0.5	$ 1.5	$ 1.4

Goodwill and Intangible Asset54

Goodwill and Intangible Assets - Schedule of Estimated Aggregate Amortization Expense (Details) $ in Thousands	Sep. 30, 2017USD ($)
Finite-Lived Intangible Assets, Net, Amortization Expense, Rolling Maturity [Abstract]
October 2017 to September 2018	$ 1,981
October 2018 to September 2019	1,981
October 2019 to September 2020	1,981
October 2020 to September 2021	1,981
October 2021 to September 2022	$ 1,598

Defined Benefit Pension Plan (D

Defined Benefit Pension Plan (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Retirement Benefits [Abstract]
Service cost	$ 0	$ 0	$ 0	$ 1,153
Interest cost	2,047	2,385	5,984	7,600
Expected return on plan assets	(3,598)	(4,324)	(10,519)	(13,778)
Prior service cost	15	0	45	0
Amortization of actuarial loss	289	0	842	0
Amortization of prior service cost	(25)	0	(71)	0
Net pension credit	$ (1,272)	$ (1,939)	$ (3,719)	$ (5,025)

Debt - Narrative (Details)

Debt - Narrative (Details)

Jul. 25, 2017

Jul. 03, 2017USD ($)

Jul. 01, 2017

Nov. 21, 2016

Jul. 01, 2015USD ($)

Sep. 27, 2012USD ($)

Sep. 30, 2017USD ($)

Sep. 30, 2016USD ($)

Oct. 02, 2017USD ($)

Jun. 21, 2017USD ($)

Jun. 20, 2017USD ($)

Dec. 31, 2016USD ($)

Jul. 02, 2015

Feb. 28, 2009USD ($)

Debt [Line Items]

Current net worth

$ 520,021,000

$ 515,142,000

$ 505,602,000

Prepayment

37,709,000

5,428,000

Interest rate swap

Debt [Line Items]

Term of derivative contract

2 years

5.25% Senior Notes, due October 1, 2022

Debt [Line Items]

Aggregate principal value of debt

$ 300,000,000

300,000,000

Stated interest rate

5.25%

Net proceeds from issuance debt

$ 294,600,000

Fair value of 2022 Senior Notes

307,500,000

Mortgages

Debt [Line Items]

Prepayment

$ 32,000,000

Mortgages | Interest rate swap

Debt [Line Items]

Term of derivative contract

2 years

Mortgages | Interest rate collar

Debt [Line Items]

Term of derivative contract

5 years

Mortgages | Cash

Debt [Line Items]

Prepayment

25,000,000

Mortgages | York Property Mortgage

Debt [Line Items]

Aggregate principal value of debt

$ 325,000,000

$ 235,000,000

Stated interest rate

10.60%

5.60%

Term of mortgage loan

7 years

7 years

Net cash proceeds from issuance of debt

$ 98,000,000

Term of amortization schedule

25 years

Minimum net worth required

$ 325,000,000

$ 325,000,000

$ 425,000,000

Maximum LTV under agreement (as a percent)

0.65

Minimum debt yield under agreement (as a percent)

8.50%

Cash Management Account balance reflected within Restricted Cash

$ 1,800,000

3,600,000

4,600,000

Mortgages | York Property Mortgage | Standard & Poor's, B Plus Rating

Debt [Line Items]

Term of required debt service

6 months

Mortgages | York Property Mortgage | Standard & Poor's, B Rating

Debt [Line Items]

Term of required debt service

12 months

Mortgages | York Property Mortgage | Interest rate swap

Debt [Line Items]

Term of derivative contract

2 years

Floor rate

3.127%

Mortgages | York Property Mortgage | Interest rate collar's floor rate

Debt [Line Items]

Term of derivative contract

5 years

Mortgages | York Property Mortgage | One-month LIBOR rate

Debt [Line Items]

Spread on variable rate

2.25%

Mortgages | Maximum

Debt [Line Items]

Prepayment

$ 25,000,000

Mortgages | Maximum | York Property Mortgage | Interest rate collar's floor rate

Debt [Line Items]

Floor rate

6.00%

Mortgages | Minimum | York Property Mortgage | Interest rate collar's floor rate

Debt [Line Items]

Floor rate

4.167%

Senior Notes

Debt [Line Items]

Debt retired

80,000,000

Senior Notes | 5.25% Senior Notes, due October 1, 2022

Debt [Line Items]

Aggregate principal value of debt

$ 300,000,000

Stated interest rate

5.25%

Convertible debt

Debt [Line Items]

Debt retired

$ 182,000,000

SFS Credit Facility

Debt [Line Items]

Maximum aggregate borrowing capacity

$ 1,035,000,000

1,035,000,000

1,035,000,000

Incremental revolving credit facility

503,132,000

554,969,000

569,021,000

Credit Agreement sub-limit

270,000,000

SFS Credit Facility | Subsequent Event

Debt [Line Items]

Reduction to borrowing capacity

$ 235,000,000

Maximum aggregate borrowing capacity

800,000,000

Credit Agreement

Debt [Line Items]

Maximum aggregate borrowing capacity

1,335,000,000

1,335,000,000

1,335,000,000

Incremental revolving credit facility

638,068,000

729,517,000

734,464,000

Credit Agreement sub-limit

320,000,000

Accordion feature (not to exceed)

150,000,000

Limitation on net outstanding auction guarantees

600,000,000

Aggregate available borrowing capacity required (equals or exceeds)

100,000,000

Liquidity Amount required (equals or exceeds)

200,000,000

Aggregate fees incurred in conjunction with the Credit Agreement

21,800,000

Unamortized fees included within Other Long-Term Assets

5,600,000

Credit Agreement | Subsequent Event

Debt [Line Items]

Maximum aggregate borrowing capacity

1,100,000,000

Agency Credit Facility

Debt [Line Items]

Maximum aggregate borrowing capacity

300,000,000

300,000,000

300,000,000

Incremental revolving credit facility

134,936,000

$ 174,548,000

$ 165,443,000

Credit Agreement sub-limit

50,000,000

Agency Credit Facility | Subsequent Event

Debt [Line Items]

Maximum aggregate borrowing capacity

$ 300,000,000

Incremental Credit Facility

Debt [Line Items]

Incremental revolving credit facility

$ 50,000,000

Term of extension to maturity date of the Incremental Facility

1 year

Term of additional extension allowed with the consent of the lenders

365 days

Sotheby's

Debt [Line Items]

Current net worth

$ 520,000,000

Debt - Summary of Information R

Debt - Summary of Information Related to the Credit Agreement (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Line of Credit Facility [Line Items]
Borrowings outstanding	$ 434,000,000	$ 553,000,000	$ 434,000,000	$ 553,000,000	$ 565,000,000
Agency Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	300,000,000	300,000,000	300,000,000	300,000,000	300,000,000
Borrowing base	134,936,000	174,548,000	134,936,000	174,548,000	165,443,000
Borrowings outstanding	0	0	0	0	0
Available borrowing capacity	134,936,000	174,548,000	134,936,000	174,548,000	165,443,000
Average borrowings outstanding	0	0	0	0	0
Borrowing Costs
Interest	0	0	0	0
Fees	777,000	640,000	2,141,000	2,028,000
Total	777,000	640,000	2,141,000	2,028,000
SFS Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	1,035,000,000	1,035,000,000	1,035,000,000	1,035,000,000	1,035,000,000
Borrowing base	503,132,000	554,969,000	503,132,000	554,969,000	569,021,000
Borrowings outstanding	434,000,000	553,000,000	434,000,000	553,000,000	565,000,000
Available borrowing capacity	69,132,000	1,969,000	69,132,000	1,969,000	4,021,000
Average borrowings outstanding	508,342,000	523,397,000	537,374,000	527,204,000	534,433,000
Borrowing Costs
Interest	4,746,000	3,694,000	13,471,000	10,824,000
Fees	1,308,000	739,000	2,698,000	2,156,000
Total	$ 6,054,000	$ 4,433,000	$ 16,169,000	$ 12,980,000
Weighted-average cost of borrowings (as a percent)	4.80%	3.40%	4.00%	3.30%
Charge associated with reduction borrowing capacity	$ 700,000		$ 700,000
Weighted-average cost of borrowings, excluding charge (as a percent)	4.20%		3.80%
Total
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 1,335,000,000	$ 1,335,000,000	$ 1,335,000,000	$ 1,335,000,000	1,335,000,000
Borrowing base	638,068,000	729,517,000	638,068,000	729,517,000	734,464,000
Borrowings outstanding	434,000,000	553,000,000	434,000,000	553,000,000	565,000,000
Available borrowing capacity	204,068,000	176,517,000	204,068,000	176,517,000	169,464,000
Average borrowings outstanding	508,342,000	523,397,000	537,374,000	527,204,000	$ 534,433,000
Borrowing Costs
Interest	4,746,000	3,694,000	13,471,000	10,824,000
Fees	2,085,000	1,379,000	4,839,000	4,184,000
Total	$ 6,831,000	$ 5,073,000	$ 18,310,000	$ 15,008,000

Debt - Schedule of Long-Term De

Debt - Schedule of Long-Term Debt (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Debt [Line Items]
Total Long-Term Debt, net	$ 557,190	$ 598,941	$ 600,485
York Property Mortgage
Debt [Line Items]
Long-term debt	272,261	309,212	310,834
Less current portion	(11,912)	(6,629)	(6,546)
Unamortized debt issuance costs, noncurrent	4,797	5,555	5,808
Unamortized debt issuance costs, current	1,010	1,010	1,010
2022 Senior Notes
Debt [Line Items]
Long-term debt	296,841	296,358	296,197
Unamortized debt issuance costs, noncurrent	$ 3,159	$ 3,642	$ 3,803

Debt - Schedule of Aggregate Fu

Debt - Schedule of Aggregate Future Principal and Interest Payments (Details) $ in Thousands	Sep. 30, 2017USD ($)
Debt Disclosure [Abstract]
October 2017 to September 2018	$ 38,233
October 2018 to September 2019	37,494
October 2019 to September 2020	471,953
October 2020 to September 2021	38,567
October 2021 to September 2022	$ 244,850

Derivative Financial Instrume60

Derivative Financial Instruments - Schedule of Fair Value Information Related to Derivative Financial Instruments (Details) - Designated as Hedging Instruments - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Derivatives, Fair Value [Line Items]
Assets	$ 238	$ 30,340	$ 20,098
Liabilities	7,901	6,115	15,347
Cash Flow Hedges
Derivatives, Fair Value [Line Items]
Assets	238	82
Liabilities	4,275	6,115	15,347
Cash Flow Hedges | Interest rate swap | Other Current Assets
Derivatives, Fair Value [Line Items]
Assets	238	82
Cash Flow Hedges | Interest rate swap | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Liabilities		163	651
Cash Flow Hedges | Interest rate collar | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Liabilities	1,375
Cash Flow Hedges | Interest rate collar | Other Long-Term Liabilities
Derivatives, Fair Value [Line Items]
Liabilities	2,900	5,952	14,696
Net Investment Hedges | Foreign exchange contracts | Other Current Assets
Derivatives, Fair Value [Line Items]
Assets		$ 30,258	20,098
Net Investment Hedges | Foreign exchange contracts | Other Current Liabilities
Derivatives, Fair Value [Line Items]
Liabilities	$ 3,626		$ 0

Derivative Financial Instrume61

Derivative Financial Instruments - Narrative (Details) - USD ($) $ in Thousands

Jul. 03, 2017

Jul. 01, 2017

Nov. 21, 2016

Jul. 01, 2015

Jun. 30, 2017

Sep. 30, 2017

Jun. 30, 2017

Sep. 30, 2016

Sep. 30, 2017

Sep. 30, 2016

Jul. 31, 2021

Dec. 31, 2016

Derivative [Line Items]

Realized net gain

$ 29,110

$ (3,308)

Initial period under interest rate protection agreements

2 years

Reduction to notional amount of derivative

$ 57,000

Annual prepayments

$ 37,709

5,428

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

7 years

Interest rate swap

Derivative [Line Items]

Term of derivative contract

2 years

Interest rate swap | Mortgages

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

$ 63,000

Interest rate collar

Derivative [Line Items]

Notional value of derivative

$ 277,100

$ 277,100

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%

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%

6.00%

Foreign exchange contracts

Derivative [Line Items]

Notional value of derivative

$ 143,900

$ 143,900

Liabilities recorded within Accounts Payable and Accrued Liabilities

400

$ 10,500

400

10,500

$ 3,600

Designated as Hedging Instruments

Derivative [Line Items]

Reduction in notional amount of derivative reclassified from Accumulated Other Comprehensive Loss into Net Income

0

0

$ (622)

0

Not Designated as Hedging Instrument | Forward exchange contracts

Derivative [Line Items]

Term of derivative contract

6 months

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

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

$ 0

$ 0

(622)

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

$ (622)

$ 0

Derivative Financial Instrume62

Derivative Financial Instruments - Summary of the Effect of the Derivative Financial Instruments (Details) - Designated as Hedging Instruments - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments
Gain (Loss) Recognized in Other Comprehensive Income (Loss) - Effective Portion	$ (793)		$ 5,471	$ (2,652)	$ 4,369
Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Effective Portion	292		192	327	631
Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Ineffective Portion	0		0	622	0
Cash Flow Hedges
Derivative Instruments
Gain (Loss) Recognized in Other Comprehensive Income (Loss) - Effective Portion	118		1,148	337	(5,727)
Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Effective Portion	292		192	327	631
Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Ineffective Portion	0		0	622	0
Cash Flow Hedges | Interest rate swap
Derivative Instruments
Gain (Loss) Recognized in Other Comprehensive Income (Loss) - Effective Portion	(7)		223	127	(860)
Cash Flow Hedges | Interest rate swap | Interest Expense
Derivative Instruments
Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Effective Portion	(8)		192	27	631
Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Ineffective Portion	0		0	0	0
Cash Flow Hedges | Interest rate collar
Derivative Instruments
Gain (Loss) Recognized in Other Comprehensive Income (Loss) - Effective Portion	125		925	210	(4,867)
Cash Flow Hedges | Interest rate collar | Interest Expense
Derivative Instruments
Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Effective Portion	300		0	300	0
Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Ineffective Portion	0		0	0	0
Cash Flow Hedges | Interest rate collar | Non-operating income
Derivative Instruments
Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Effective Portion				0	0
Amount Reclassified from Accumulated Other Comprehensive Loss into Net (Loss) Income - Ineffective Portion		$ (600)		622	0
Net Investment Hedges | Foreign exchange contracts
Derivative Instruments
Gain (Loss) Recognized in Other Comprehensive Income (Loss) - Effective Portion	$ (911)		$ 4,323	$ (2,989)	$ 10,096

Sale of Pink Diamond (Details)

Sale of Pink Diamond (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	Apr. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016	Jun. 30, 2016
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
Total purchase price		$ 81,501	$ 24,359	$ 172,815	$ 36,434
Carrying value of the Pink Diamond		63,319	179,564	63,319	179,564	$ 159,043
Cost of Inventory Sales		78,734	$ 29,616	172,396	$ 47,735
Pink Diamond
Product Information [Line Items]
Total purchase price	$ 71,200
Carrying value of the Pink Diamond		68,400		68,400
Gain on sale of Pink Diamond	$ 400
Cost of Inventory Sales		$ 70,800		$ 70,800

Supplemental Condensed Consol64

Supplemental Condensed Consolidated Balance Sheet Information - Schedule of Prepaid Expenses and Other Current Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Prepaid expenses	$ 31,623	$ 20,436	$ 29,716
Derivative financial instruments (see Note 8)	239	30,340	20,098
Other	23,661	25,831	16,052
Total Prepaid Expenses and Other Current Assets	$ 55,523	$ 76,607	$ 65,866

Supplemental Condensed Consol65

Supplemental Condensed Consolidated Balance Sheet Information - Narrative (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Derivative Instruments
Realized net gain	$ 29,110	$ (3,308)
Designated as Hedging Instruments | Foreign exchange contracts | Net investment hedges
Derivative Instruments
Aggregate notional value	213,800
Realized net gain	$ 29,100

Supplemental Condensed Consol66

Supplemental Condensed Consolidated Balance Sheet Information - Schedule of Other Long-Term Assets (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Schedule of Equity Method Investments [Line Items]
Defined benefit pension plan asset (see Note 6)	$ 90,559	$ 78,576	$ 63,563
Equity method investments	46,207	43,143	41,695
Trust assets related to deferred compensation liability	25,325	26,713	27,962
Restricted cash	17,835	1,064	1,127
Other	16,156	15,928	16,191
Total Other Long-Term Assets	196,082	$ 165,424	$ 150,538
Funds held in escrow	15,300
Other equity method investment
Schedule of Equity Method Investments [Line Items]
Equity method investments	$ 5,400
Ownership interest	50.00%

Supplemental Condensed Consol67

Supplemental Condensed Consolidated Balance Sheet Information - Schedule of Other Long-Term Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Deferred compensation liability	$ 24,563	$ 25,914	$ 26,086
Acquisition earn-out consideration (see Note 19)	17,500	26,250	0
Interest rate collar liability (see Note 8)	2,900	5,952	14,696
Other	6,704	6,964	7,010
Total Other Long-Term Liabilities	$ 51,667	$ 65,080	$ 47,792

Supplemental Condensed Consol68

Supplemental Condensed Consolidated Cash Flow Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
(Increase) decrease in:
Prepaid expenses and other current assets	$ (2,443)	$ (7,974)
Other long-term assets	788	10,748
Income tax receivables and deferred income tax assets	(34,168)	11,835
Decrease in:
Accrued income taxes and deferred income tax liabilities	(15,156)	(20,220)
Accounts payable and accrued liabilities and other liabilities	(64,697)	(11,841)
Total changes in other operating assets and liabilities	$ (115,676)	$ (17,452)

Shareholders' Equity and Divi69

Shareholders' Equity and Dividends - Schedule of Information Regarding Common Stock Repurchase Program (Details) - USD ($) $ / shares in Units, $ in Thousands	2 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016
Equity [Abstract]
Shares repurchased (in shares)	0	866,000	11,093,000
Aggregate purchase price		$ 40,193	$ 286,084
Average price per share (in dollars per share)		$ 46.40	$ 25.79

Shareholders' Equity and Divi70

Shareholders' Equity and Dividends - Narrative (Details) - USD ($)	Aug. 15, 2017	Jan. 29, 2014	Sep. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Dividends Payable [Line Items]
Increase to share repurchase authorization	$ 100,000,000
Aggregate share repurchase authorization	$ 100,030,000
Shares repurchased (in shares)			0			866,000	11,093,000
Remaining under current share repurchase authorization			$ 100,030,000	$ 100,030,000		$ 100,030,000
Special dividend declared (in dollars per share)				$ 0	$ 0	$ 0	$ 0
Accrued dividend equivalents paid upon vesting						$ 2,000,000	$ 1,400,000
Special dividend
Dividends Payable [Line Items]
Special dividend declared		$ 300,000,000
Special dividend declared (in dollars per share)		$ 4.34
Dividends accrued		$ 11,000,000

Accumulated Other Comprehensi71

Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Increase (Decrease) in Stockholders' Equity
Balance at beginning of period			$ 505,602
Reclassifications from accumulated other comprehensive gain (loss), net of tax	$ 511	$ 192	1,591	$ 631
Total other comprehensive income (loss)	3,155	1,122	10,727	(17,546)
Balance at end of period	520,021	515,142	520,021	515,142
AOCI Attributable to Parent
Increase (Decrease) in Stockholders' Equity
Balance at end of period	(79,631)	(83,750)	(79,631)	(83,750)
Currency Translation Adjustments
Increase (Decrease) in Stockholders' Equity
Balance at beginning of period	(80,327)	(71,274)	(89,478)	(52,279)
Other comprehensive income (loss) before reclassifications, net of tax	3,870	(4,895)	13,021	(23,890)
Other comprehensive income (loss) before reclassifications, tax	851	(4,946)	2,272	(7,691)
Total other comprehensive income (loss)	3,870	(4,895)	13,021	(23,890)
Balance at end of period	(76,457)	(76,169)	(76,457)	(76,169)
Cash Flow & Net Investment Hedges | Cash Flow Hedges
Increase (Decrease) in Stockholders' Equity
Balance at beginning of period	(2,788)	(10,742)	(3,664)	(4,306)
Other comprehensive income (loss) before reclassifications, net of tax	118	1,148	337	(5,727)
Other comprehensive income (loss) before reclassifications, tax	72	710	207	(3,550)
Reclassifications from accumulated other comprehensive gain (loss), net of tax	292	192	949	631
Reclassifications from accumulated other comprehensive gain (loss), tax	181	119	588	391
Total other comprehensive income (loss)	410	1,340	1,286	(5,096)
Balance at end of period	(2,378)	(9,402)	(2,378)	(9,402)
Cash Flow & Net Investment Hedges | Net Investment Hedges
Increase (Decrease) in Stockholders' Equity
Balance at beginning of period	14,540	5,773	16,618	0
Other comprehensive income (loss) before reclassifications, net of tax	(911)	4,323	(2,989)	10,096
Other comprehensive income (loss) before reclassifications, tax	(552)	2,817	(1,822)	6,694
Total other comprehensive income (loss)	(911)	4,323	(2,989)	10,096
Balance at end of period	13,629	10,096	13,629	10,096
Defined Benefit Pension Plan
Increase (Decrease) in Stockholders' Equity
Balance at beginning of period	(14,211)	(8,629)	(13,834)	(9,619)
Reclassifications from accumulated other comprehensive gain (loss), net of tax	219	0	642	0
Reclassifications from accumulated other comprehensive gain (loss), tax	45	0	129	0
Total other comprehensive income (loss)	(214)	354	(591)	1,344
Balance at end of period	(14,425)	(8,275)	(14,425)	(8,275)
Currency translation adjustments
Increase (Decrease) in Stockholders' Equity
Other comprehensive income (loss) before reclassifications, net of tax	433	(354)	1,233	(1,263)
Net actuarial gain, net of tax of $0, $0, $0, and ($81)
Increase (Decrease) in Stockholders' Equity
Reclassifications from accumulated other comprehensive gain (loss), net of tax	0	0	0	81
Reclassifications from accumulated other comprehensive gain (loss), tax	0	0	0	(81)
Prior service cost amortization, net of tax of ($5), $0, ($12), and $0
Increase (Decrease) in Stockholders' Equity
Reclassifications from accumulated other comprehensive gain (loss), net of tax	(20)	0	(59)	0
Reclassifications from accumulated other comprehensive gain (loss), tax	(5)	0	(12)	0
Actuarial loss amortization, net of tax of $50, $0, $141, and $0
Increase (Decrease) in Stockholders' Equity
Reclassifications from accumulated other comprehensive gain (loss), net of tax	239	0	701	0
Reclassifications from accumulated other comprehensive gain (loss), tax	$ 50	$ 0	$ 141	$ 0

Accumulated Other Comprehensi72

Accumulated Other Comprehensive Loss - Summary of Reclassification Adjustments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustments, net of tax	$ 511	$ 192	$ 1,591	$ 631
Defined Benefit Pension Plan
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment, before tax	264	0	771	0
Tax effect	(45)	0	(129)	0
Reclassification adjustments, net of tax	219	0	642	0
Prior service cost amortization
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment, before tax	(25)	0	(71)	0
Tax effect	5	0	12	0
Reclassification adjustments, net of tax	(20)	0	(59)	0
Actuarial loss amortization
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment, before tax	289	0	842	0
Tax effect	(50)	0	(141)	0
Reclassification adjustments, net of tax	239	0	701	0
Reclassification out of Accumulated Other Comprehensive Income | Cash Flow Hedges
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Reclassification adjustment, before tax	473	311	1,537	1,022
Tax effect	(181)	(119)	(588)	(391)
Reclassification adjustments, net of tax	$ 292	$ 192	$ 949	$ 631

Commitments and Contingencies (

Commitments and Contingencies (Details) - USD ($) $ in Millions	Nov. 02, 2017	Sep. 30, 2017
Commitments and Contingencies Disclosure [Abstract]
Aggregate remaining commitment for salaries and other cash compensation, excluding any participation in incentive compensation programs		$ 13.9
Sales proceeds related to property offered at auction
Guarantor Obligations [Line Items]
Outstanding guarantees of collection with pre-sale low estimates		$ 2.5
Subsequent Event | Sales proceeds related to property offered at auction
Guarantor Obligations [Line Items]
Reduction to obligation under guarantees of collection	$ 1.8

Uncertain Tax Positions (Detail

Uncertain Tax Positions (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Income Tax Disclosure [Abstract]
Unrecognized tax benefits, excluding interest and penalties	$ 14.2	$ 19.5	$ 19.7
Net decrease in unrecognized tax benefits	5.3
Unrecognized tax benefits that would favorably affect effective income tax rate	3.1	$ 9.3	$ 13.7
Reasonably possible decrease in balance of unrecognized tax benefits within 12 months	3
Decrease to accrual for interest and penalties	$ 0.1

Auction Guarantees (Details)

Auction Guarantees (Details) - USD ($)	Nov. 02, 2017	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016
Guarantor Obligations [Line Items]
Outstanding auction guarantees		$ 139,600,000
Irrevocable bids		27,600,000
Auction guarantee advances outstanding		1,100,000	$ 1,000,000	$ 2,300,000
Estimated fair value of obligation to perform under outstanding auction guarantees		5,000,000	$ 600,000	$ 6,200,000
Subsequent Event
Guarantor Obligations [Line Items]
Outstanding auction guarantees	$ 246,800,000
Irrevocable bids	109,400,000
Auction guarantee advances outstanding	$ 11,300,000
Credit Agreement
Guarantor Obligations [Line Items]
Limitation on net outstanding auction guarantees		$ 600,000,000

Share-Based Payments - Schedule

Share-Based Payments - Schedule of Compensation Expense for Share-Based Payments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based payment expense (pre-tax)	$ 5,408	$ 2,560	$ 17,423	$ 10,048
Total share-based payment expense (after-tax)	3,657	1,984	11,654	7,394
Salaries and related costs
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based payment expense (pre-tax)	5,408	2,743	17,423	10,871
Voluntary separation incentive programs | Voluntary separation incentive programs
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total share-based payment expense (pre-tax)	$ 0	$ (183)	$ 0	$ (823)

Share-Based Payments - Narrativ

Share-Based Payments - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Credits related to the voluntary separation incentive programs	$ 5,408	$ 2,560	$ 17,423	$ 10,048
Excess tax benefit related to share-based payments			2,600
Tax shortfall related to share-based payments				(1,300)
Unrecognized compensation expense related to the unvested portion of share-based payments	$ 27,500		$ 27,500
Weighted average period of amortization			2 years 2 months 24 days
Shares granted (in shares)			775,000
Stock options expiration period			10 years
Options outstanding and exercisable (in shares)	50,000		50,000
Weighted average exercise price (in dollars per share)	$ 22.11		$ 22.11
Weighted average remaining contractual term			2 years 4 months 9 days
Aggregate intrinsic value	$ 1,200		$ 1,200
Number of deferred stock units outstanding (in shares)	1,990,000		1,990,000		2,235,000
Company's Incentive Compensation Programs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value			$ 31,000
Director's Stock Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Credits related to the voluntary separation incentive programs	$ 300	300	$ 800	800
Shares available for future awards (in shares)	120,337		120,337
Number of deferred stock units outstanding (in shares)	164,089		164,089
Restricted Stock Units (RSUs)
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Shares available for future awards (in shares)	2,300,000		2,300,000
Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Restricted Shares, RSU's And PSU's
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Aggregate fair value of RSU's and PSU's that vested			$ 39,500	$ 15,000
Stock Options
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Shares available for future awards (in shares)	104,100		104,100
Stock options exercised (in shares)			0	0
Stock options granted (in shares)			0	0
Minimum | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Maximum | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			4 years
Cliff Vesting | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grant date fair value			$ 14,600
Shares granted (in shares)			369,897
Cliff Vesting | Minimum | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total maximum vesting opportunity of initial award (as a percent)			100.00%
Cliff Vesting | Maximum | Performance Shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares granted (in shares)			739,794
Total maximum vesting opportunity of initial award (as a percent)			200.00%
Incremental Vesting | Restricted Stock Units (RSUs) | Company's Incentive Compensation Programs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period			3 years
Grant date fair value			$ 16,400
Shares granted (in shares)			404,785
Voluntary separation incentive programs | Voluntary separation incentive programs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Credits related to the voluntary separation incentive programs	$ 0	$ (183)	$ 0	$ (823)

Share-Based Payments - Schedu78

Share-Based Payments - Schedule of Changes to the Number of Outstanding RSU's, PSU's, and Restricted Shares (Details) shares in Thousands	9 Months Ended
	Sep. 30, 2017$ / sharesshares
Restricted Shares, RSU's and PSU's
Outstanding, beginning balance (in shares) | shares	2,235
Granted (in shares) | shares	775
Vested (in shares) | shares	(834)
Canceled (in shares) | shares	(186)
Outstanding, ending balance (in shares) | shares	1,990
Weighted Average Grant Date Fair Value
Outstanding, beginning balance (in dollars per share) | $ / shares	$ 36.40
Granted (in dollars per share) | $ / shares	39.92
Vested (in dollars per share) | $ / shares	39.25
Canceled (in dollars per share) | $ / shares	38.77
Outstanding, ending balance (in dollars per share) | $ / shares	$ 34.95

(Loss) Earnings Per Share - Nar

(Loss) Earnings Per Share - Narrative (Details) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Potential common shares excluded from computation of diluted earnings per share	1	1	1	1

(Loss) Earnings Per Share - Com

(Loss) Earnings Per Share - Computation Of Basic And Diluted (Loss) Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Numerator:
Net (loss) income attributable to Sotheby’s	$ (23,479)	$ (54,470)	$ 42,087	$ 8,610
Less: Net income attributable to participating securities	0	0	643	115
Net (loss) income attributable to Sotheby’s common shareholders	$ (23,479)	$ (54,470)	$ 41,444	$ 8,495
Denominator:
Weighted average common shares outstanding (in shares)	52,532	55,013	52,755	58,379
Basic (loss) earnings per share - Sotheby’s common shareholders (in dollars per share)	$ (0.45)	$ (0.99)	$ 0.79	$ 0.15
Numerator:
Net (loss) income attributable to Sotheby’s	$ (23,479)	$ (54,470)	$ 42,087	$ 8,610
Less: Net income attributable to participating securities	0	0	643	115
Net (loss) income attributable to Sotheby’s common shareholders	$ (23,479)	$ (54,470)	$ 41,444	$ 8,495
Weighted average effect of dilutive potential common shares:
Performance share units (in shares)	0	0	243	433
Deferred stock units (in shares)	0	0	159	150
Stock options (in shares)	0	0	26	13
Weighted average dilutive potential common shares outstanding (in shares)	0	0	428	596
Weighted average diluted shares outstanding (in shares)	52,532	55,013	53,183	58,975
Diluted (loss) earnings per share - Sotheby's common shareholders (in dollars per share)	$ (0.45)	$ (0.99)	$ 0.78	$ 0.14

Acquisition of Art Agency, Pa81

Acquisition of Art Agency, Partners - Narrative (Details) $ in Thousands	Jan. 11, 2016USD ($)	Sep. 30, 2016USD ($)	Jun. 30, 2016USD ($)	Mar. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)annual_incremental_payment
Business Acquisition [Line Items]
Remaining liability		$ 0				$ 17,500	$ 0	$ 26,250
Goodwill allocated						0	34,490
Agency
Business Acquisition [Line Items]
Goodwill allocated			$ 28,300			0	28,339
All Other
Business Acquisition [Line Items]
Goodwill allocated			$ 6,200			$ 0	6,151
Tax deductible period						15 years
Art Agency, Partners
Business Acquisition [Line Items]
Initial cash consideration	$ 50,000
Transaction costs incurred	$ 800
Art Agency, Partners | General and Administrative Expenses
Business Acquisition [Line Items]
Transaction costs recognized				$ 200	$ 600
Art Agency, Partners | Former principals of AAP
Business Acquisition [Line Items]
Term of employment agreement	5 years
Period that non-competition and non-solicitation agreements continue in effect following the end of employment	12 months
Art Agency, Partners | Earn Out
Business Acquisition [Line Items]
Compensation expense related to earn-out arrangement	$ 35,000	$ 17,200					$ 21,600	$ 35,000
Number of annual incremental payments | annual_incremental_payment								4
Accrued liability due in the first quarter of 2018						$ 8,750
Remaining liability						$ 17,500
Art Agency, Partners | Minimum | Earn Out
Business Acquisition [Line Items]
Performance period following acquisition	4 years
Art Agency, Partners | Maximum | Earn Out
Business Acquisition [Line Items]
Amount of annual incremental payments								$ 8,750

Acquisition of Art Agency, Pa82

Acquisition of Art Agency, Partners - Summary of the Allocation of the Total Purchase Price Paid for AAP (Details) - USD ($) $ in Thousands	Jan. 11, 2016	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Allocation of purchase price:
Goodwill (see Note 5)		$ 50,496	$ 50,029	$ 47,833	$ 13,621
Art Agency, Partners
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 (see Note 5)	34,490
Deferred tax assets	1,094
Total purchase price	51,189
Art Agency, Partners | Customer relationships
Allocation of purchase price:
Intangible assets	10,800
Art Agency, Partners | Non-compete agreements
Allocation of purchase price:
Intangible assets	$ 3,060

Related Party Transactions (Det

Related Party Transactions (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Related Party Transactions [Abstract]
Agency Commissions and Fees (less than for the three months ended September 30, 2017)	$ 100	$ 100	$ 4,700	$ 700
Related Party Transaction [Line Items]
Amounts owed to related party consignors	376,108	389,287	376,108	389,287	$ 511,876
Included in Accounts Receivable (net)	100		100		1,800
Related Party Consignors
Related Party Transaction [Line Items]
Amounts owed to related party consignors	$ 400	$ 900	$ 400	$ 900	$ 3,600

Uncategorized Items - bid-20170

Label	Element	Value
Mortgages [Member] | Cash [Member]
Repayments of First Mortgage Bond	us-gaap_RepaymentsOfFirstMortgageBond	$ 7,000,000