Greenhill & Co (GHL) 10-Q 9 Nov 17 2017 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2017	Nov. 01, 2017
Document Documentand Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	Q3
Trading Symbol	GHL
Entity Registrant Name	GREENHILL & CO INC
Entity Central Index Key	1,282,977
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		26,263,397

Condensed Consolidated Statemen

Condensed Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents ($4.5 million and $4.3 million restricted from use at September 30, 2017 and December 31, 2016, respectively)	$ 50,875	$ 98,313
Advisory fees receivable, net of allowance for doubtful accounts of $0.3 million and $0.0 million at September 30, 2017 and December 31, 2016, respectively	54,342	68,140
Subscription receivable	20,000	0
Other receivables	3,734	2,830
Property and equipment, net of accumulated depreciation of $61.3 million and $59.0 million at September 30, 2017 and December 31, 2016, respectively..............................................................	8,471	8,764
Goodwill	218,216	208,186
Deferred tax asset, net	60,935	62,108
Other assets	7,898	8,341
Total assets	424,471	456,682
Liabilities and Equity
Compensation payable	18,103	37,527
Accounts payable and accrued expenses	10,068	9,297
Current income taxes payable	5,486	18,968
Bank revolving loan payable	83,775	64,070
Bank term loans payable	0	16,875
Contingent obligation due selling unitholders of Cogent	9,456	15,095
Deferred tax liability	4,764	3,667
Total liabilities	131,652	165,499
Common stock, par value $0.01 per share; 100,000,000 shares authorized, 43,643,020 and 41,377,614 shares issued as of September 30, 2017 and December 31, 2016, respectively; 30,797,857 and 28,981,189 shares outstanding as of September 30, 2017 and December 31, 2016, respectively	437	414
Restricted stock units	75,422	85,907
Additional paid-in capital	797,197	734,728
Exchangeable shares of subsidiary; 257,156 shares issued as of September 30, 2017 and December 31, 2016; 32,804 shares outstanding as of September 30, 2017 and December 31, 2016	1,958	1,958
Retained earnings	65,196	111,798
Accumulated other comprehensive income (loss)	(23,127)	(32,398)
Treasury stock, at cost, par value $0.01 per share; 12,845,163 and 12,396,425 shares as of September 30, 2017 and December 31, 2016, respectively	(624,264)	(611,224)
Stockholders’ equity	292,819	291,183
Total liabilities and equity	$ 424,471	$ 456,682

Condensed Consolidated Stateme3

Condensed Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Millions	Sep. 30, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Cash and cash equivalents, restricted from use	$ 4.5	$ 4.3
Advisory fees receivable, allowance for doubtful accounts	0.3	0
Property and equipment, accumulated depreciation	$ 61.3	$ 59
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Common stock, shares authorized (shares)	100,000,000	100,000,000
Common stock, shares issued (shares)	43,643,020	41,377,614
Common stock, shares outstanding (shares)	30,797,857	28,981,189
Exchangeable shares of subsidiary, shares issued (shares)	257,156	257,156
Exchangeable shares of subsidiary, shares outstanding (shares)	32,804	32,804
Treasury stock, par value (usd per share)	$ 0.01	$ 0.01
Treasury stock, shares (shares)	12,845,163	12,396,425

Condensed Consolidated Stateme4

Condensed Consolidated Statements of Income (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Revenues
Advisory revenues	$ 48,080	$ 76,487	$ 171,818	$ 233,305
Investment revenues	12	91	472	623
Total revenues	48,092	76,578	172,290	233,928
Expenses
Employee compensation and benefits	37,178	40,746	120,071	129,362
Occupancy and equipment rental	5,300	5,052	15,298	14,602
Depreciation and amortization	777	793	2,323	2,432
Information services	2,459	2,208	7,093	6,718
Professional fees	1,877	1,806	5,488	5,064
Travel related expenses	3,488	3,129	9,702	8,903
Interest expense	873	896	2,481	2,444
Other operating expenses	6,418	2,748	8,362	8,880
Total expenses	58,370	57,378	170,818	178,405
Income (loss) before taxes	(10,278)	19,200	1,472	55,523
Provision (benefit) for taxes	(4,366)	6,090	1,885	18,428
Net income (loss) allocated to common stockholders	$ (5,912)	$ 13,110	$ (413)	$ 37,095
Average shares outstanding:
Basic (shares)	32,280,535	31,686,347	32,371,356	31,953,530
Diluted (shares)	32,280,535	31,693,173	32,371,356	31,960,892
Earnings (loss) per share:
Basic (usd per share)	$ (0.18)	$ 0.41	$ (0.01)	$ 1.16
Diluted (usd per share)	(0.18)	0.41	(0.01)	1.16
Dividends declared and paid per share (usd per share)	$ 0.45	$ 0.45	$ 1.35	$ 1.35

Condensed Consolidated Stateme5

Condensed Consolidated Statements of Comprehensive Income (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net income (loss) allocated to common stockholders	$ (5,912)	$ 13,110	$ (413)	$ 37,095
Currency translation adjustment, net of tax	2,541	805	9,271	1,765
Comprehensive income (loss) allocated to common stockholders	$ (3,371)	$ 13,915	$ 8,858	$ 38,860

Condensed Consolidated Stateme6

Condensed Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Restricted Stock UnitsRestricted Stock Units	Additional Paid-in Capital	Exchangeable Shares of Subsidiary	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock
Beginning Balance at Dec. 31, 2015		$ 405	$ 84,969	$ 697,607	$ 1,958	$ 109,860	$ (28,405)	$ (583,038)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued		9		44,789
Stock subscribed during period, value		0		0
Restricted stock units recognized, net of forfeitures			45,880
Restricted stock units delivered			(44,942)
Tax (expense) from the delivery of restricted stock units				(7,668)
Exchangeable shares of subsidiary delivered					0
Dividends						(61,609)
Tax benefit from payment of restricted stock unit dividends						2,785
Net income (loss) allocated to common stockholders						60,762
Currency translation adjustment, net of tax							(3,993)
Repurchased								(28,186)
Ending Balance at Dec. 31, 2016	$ 291,183	414	85,907	734,728	1,958	111,798	(32,398)	(611,224)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued		11		41,634
Stock subscribed during period, value		12		19,988
Restricted stock units recognized, net of forfeitures			31,740
Restricted stock units delivered			(42,225)
Tax (expense) from the delivery of restricted stock units				847
Exchangeable shares of subsidiary delivered					0
Dividends						(46,189)
Tax benefit from payment of restricted stock unit dividends						0
Net income (loss) allocated to common stockholders	(413)					(413)
Currency translation adjustment, net of tax	9,271						9,271
Repurchased								(13,040)
Ending Balance at Sep. 30, 2017	$ 292,819	$ 437	$ 75,422	$ 797,197	$ 1,958	$ 65,196	$ (23,127)	$ (624,264)

Condensed Consolidated Stateme7

Condensed Consolidated Statements of Changes in Stockholders' Equity (Parenthetical) - $ / shares	Sep. 30, 2017	Dec. 31, 2016
Common stock, par value (usd per share)	$ 0.01	$ 0.01
Treasury stock, par value (usd per share)	0.01	0.01
Common Stock
Common stock, par value (usd per share)	0.01	0.01
Treasury Stock
Treasury stock, par value (usd per share)	$ 0.01	$ 0.01

Condensed Consolidated Stateme8

Condensed Consolidated Statements of Cash Flows (unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Operating activities:
Net income (loss) allocated to common stockholders	$ (413)	$ 37,095
Non-cash items included in net income allocated to common stockholders:
Depreciation and amortization	2,323	2,432
Net investment (gains) losses	265	106
Restricted stock units recognized	31,740	31,753
Deferred taxes	(2,816)	(3,068)
Loss (gain) on fair value of contingent obligation	(5,639)	1,422
Changes in operating assets and liabilities:
Advisory fees receivable	13,798	(12,200)
Other receivables and assets	(947)	(2,184)
Deferred tax asset, net	0	7,679
Compensation payable	(19,424)	(1,340)
Accounts payable and accrued expenses	191	924
Current income taxes payable	(13,482)	(3,220)
Net cash provided by operating activities	5,596	59,399
Investing activities:
Distributions from investments	222	0
Purchases of property and equipment	(1,674)	(1,332)
Net cash used in investing activities	(1,452)	(1,332)
Financing activities:
Proceeds from revolving bank loan	69,355	83,229
Repayment of revolving bank loan	(49,650)	(60,529)
Repayment of bank term loans	(16,875)	(16,875)
Dividends paid	(46,190)	(46,432)
Purchase of treasury stock	(13,040)	(20,676)
Net tax (cost) from the delivery of restricted stock units and payment of dividend equivalents	0	(5,408)
Net cash used in financing activities	(56,400)	(66,691)
Effect of exchange rate changes on cash and cash equivalents	4,818	(5,519)
Net decrease in cash and cash equivalents	(47,438)	(14,143)
Cash and cash equivalents, beginning of period	98,313	69,962
Cash and cash equivalents, end of period	50,875	55,819
Supplemental disclosure of cash flow information:
Cash paid for interest	2,469	2,278
Cash paid for taxes, net of refunds	$ 18,538	$ 19,814

Organization

Organization	9 Months Ended
	Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Organization Greenhill & Co., Inc. and subsidiaries (the "Company" or "Greenhill") is a leading independent investment bank that provides financial and strategic advice on significant domestic and cross-border mergers and acquisitions, restructurings, financings, capital raisings and other strategic transactions to a diverse client base, including corporations, partnerships, institutions and governments globally. We act for clients located throughout the world from our global offices in the United States, Australia, Brazil, Canada, Germany, Hong Kong, Japan, Sweden, and the United Kingdom. The Company's wholly-owned subsidiaries provide advisory services in various jurisdictions. Our most significant operating entities include: Greenhill & Co., LLC (“G&Co”), Greenhill & Co. International LLP (“GCI”), Greenhill & Co. Europe LLP ("GCE"), Greenhill & Co. Australia Pty Limited (“Greenhill Australia”) and Greenhill Cogent, LP ("GC LP"). G&Co is engaged in investment banking activities principally in the United States. G&Co is registered as a broker-dealer with the Securities and Exchange Commission (“SEC”) and the Financial Industry Regulatory Authority (“FINRA”), and is licensed in all 50 states and the District of Columbia. GCI and GCE are engaged in investment banking activities in the United Kingdom and Europe, respectively, and are subject to regulation by the U.K. Financial Conduct Authority (“FCA”). Greenhill Australia engages in investment banking activities in Australia and New Zealand and is licensed and subject to regulation by the Australian Securities and Investment Commission (“ASIC”). GC LP is engaged in capital advisory services to institutional investors principally in the United States and is registered as a broker-dealer with the SEC and FINRA. The Company also operates in other locations throughout the world which are subject to regulation by other governmental and regulatory bodies and self-regulatory authorities.

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Financial Information These condensed consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States (U.S. GAAP), which require management to make estimates and assumptions regarding future events that affect the amounts reported in our financial statements and these footnotes, including investment valuations, compensation accruals and other matters. Management believes that the estimates used in preparing its condensed consolidated financial statements are reasonable and prudent. Actual results could differ materially from those estimates. Certain reclassifications have been made to prior year information to conform to current year presentation. The condensed consolidated financial statements of the Company include all consolidated accounts of Greenhill & Co., Inc. and all other entities in which the Company has a controlling interest after eliminations of all significant inter-company accounts and transactions. These condensed consolidated financial statements are unaudited and should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2016 included in the Company's Annual Report on Form 10-K filed with the SEC. The condensed consolidated financial information as of December 31, 2016 has been derived from audited consolidated financial statements not included herein. The results of operations for interim periods are not necessarily indicative of results for the entire year. Revenue Recognition Advisory Revenues It is the Company's accounting policy to recognize revenue when (i) there is persuasive evidence of an arrangement with a client, (ii) the agreed-upon services have been completed and delivered to the client or the transaction or events noted in the engagement letter are determined to be substantially complete, (iii) fees are fixed and determinable, and (iv) collection is reasonably assured. The Company recognizes advisory fee revenues for mergers and acquisitions or financing advisory and restructuring engagements when the services related to the underlying transactions are completed in accordance with the terms of the engagement letter and all other requirements for revenue recognition are satisfied. The Company recognizes capital advisory fees from primary capital raising transactions at the time of the client's acceptance of capital or capital commitments to a fund in accordance with the terms of the engagement letter. Generally, fee revenue is determined based upon a fixed percentage of capital committed to the fund. For multiple closings, revenue is recognized at each interim closing based on the amount of capital committed at each closing at the fixed fee percentage. At the final closing, revenue is recognized at the fixed percentage for the amount of capital committed since the last interim closing. The Company recognizes capital advisory fees from secondary market transactions at the time the sale or transfer of the capital interest is completed in accordance with the terms of the engagement letter. Generally, fee revenue is determined based upon a fixed percentage of the transaction value. While the majority of the Company's fee revenue is earned at the conclusion of a transaction or closing of a fund, on-going retainer fees, substantially all of which relate to non-success based strategic advisory and financing advisory and restructuring assignments, are also earned and recognized as advisory fee revenue over the period in which the related service is rendered. The Company’s clients reimburse certain expenses incurred by the Company in the conduct of advisory engagements. Expenses are reported net of such client reimbursements. Client reimbursements totaled $1.0 million and $1.4 million for the three months ended September 30, 2017 and 2016 , respectively, and $3.0 million and $4.6 million for the nine months ended September 30, 2017 and 2016 , respectively. Investment Revenues Investment revenues consist of gains (or losses) on the Company's investments in certain merchant banking funds and interest income. The Company recognizes revenue on its investments in merchant banking funds based on its allocable share of realized and unrealized gains (or losses) reported by such funds. Cash and Cash Equivalents The Company’s cash and cash equivalents consist of (i) cash held on deposit with financial institutions, (ii) cash equivalents and (iii) restricted cash. The Company maintains its cash and cash equivalents with financial institutions with high credit ratings. The Company considers all highly liquid investments with a maturity date of three months or less, when purchased, to be cash equivalents. Cash equivalents primarily consist of money market funds and overnight deposits. Management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. See "Note 3 — Cash and Cash Equivalents". Advisory Fees Receivables Receivables are stated net of an allowance for doubtful accounts. The estimate for the allowance for doubtful accounts is derived by the Company by utilizing past client transaction history and an assessment of the client’s creditworthiness. The Company recorded bad debt expense of $0.3 million and $1.1 million for the three and nine month periods ended September 30, 2017 , respectively. The Company recorded bad debt expense of $0.0 million and $0.4 million for the three and nine month periods ended September 30, 2016 , respectively. Included in the advisory fees receivable balance at September 30, 2017 and December 31, 2016 were $28.5 million and $26.1 million , respectively, of long term receivables related to primary capital advisory engagements which are generally paid in installments over a period of three years . Included as a component of investment revenues on the condensed consolidated statements of income is interest income related to primary capital advisory engagements of $0.2 million and $0.1 million for the three month periods ended September 30, 2017 and 2016 , respectively, and $0.5 million and $0.6 million for the nine month periods ended September 30, 2017 and 2016 , respectively. Credit risk related to advisory fees receivable is disbursed across a large number of clients located in various geographic areas. The Company controls credit risk through credit approvals and monitoring procedures but does not require collateral to support accounts receivable. Goodwill Goodwill is the cost in excess of the fair value of identifiable net assets at acquisition date. The Company tests its goodwill for impairment at least annually. An impairment loss is triggered if the estimated fair value of an operating unit is less than estimated net book value. Such loss is calculated as the difference between the estimated fair value of goodwill and its carrying value. Goodwill is translated at the rate of exchange prevailing at the end of the periods presented in accordance with the accounting guidance for foreign currency translation. Any translation gain or loss is included in the foreign currency translation adjustment, which is included as a component of other comprehensive income in the condensed consolidated statements of changes in stockholders' equity. Other Assets Included in other assets are the Company's investments in merchant banking funds, which are recorded under the equity method of accounting, based upon the Company's proportionate share of the estimated fair value of the underlying merchant banking fund's net assets. The value of merchant banking fund investments is determined by management of the fund after giving consideration to the cost of the security, quoted market prices, the pricing of other sales of securities by the portfolio company, the price of securities of other companies comparable to the portfolio company, purchase multiples paid in other comparable third-party transactions, the original purchase price multiple, market conditions, liquidity, operating results and other qualitative and quantitative factors. The funds may apply discounts to reflect the lack of liquidity and other transfer restrictions. Restricted Stock Units The Company accounts for its share-based compensation payments by recording the fair value of restricted stock units granted to employees as compensation expense. The restricted stock units are generally amortized over a four to five -year service period following the date of grant. Compensation expense is determined based upon the fair market value of the Company’s common stock at the date of grant. As the Company expenses the awards, the restricted stock units recognized are recorded within stockholders' equity. The restricted stock units are reclassified into common stock and additional paid-in capital upon vesting. The Company records as treasury stock the repurchase of stock delivered to its employees in settlement of tax liabilities incurred upon the vesting of restricted stock units. The Company records dividend equivalent payments on outstanding restricted stock units as a dividend payment and a charge to stockholders' equity. Earnings per Share The Company calculates basic earnings per share (“EPS”) by dividing net income allocated to common stockholders by the sum of (i) the weighted average number of shares outstanding for the period and (ii) the weighted average number of shares deemed issuable due to the vesting of restricted stock units for accounting purposes. See "Note 8 — Equity". The Company calculates diluted EPS by dividing net income allocated to common stockholders by the sum of (i) basic shares per above and (ii) the dilutive effect of the common stock deliverable pursuant to restricted stock units for which future service is required. Under the treasury method, the number of shares issuable upon the vesting of restricted stock units included in the calculation of diluted EPS is the excess, if any, of the number of shares expected to be issued, less the number of shares that could be purchased by the Company with the proceeds to be received upon settlement at the average market closing price during the reporting period. See "Note 9 — Earnings per Share". Provision for Taxes The Company accounts for taxes in accordance with the accounting guidance for income taxes which requires the recognition of tax benefits or expenses on the temporary differences between the financial reporting and tax bases of its assets and liabilities. Additionally, the Company accounts for the net tax (cost) from the delivery of restricted stock units and payment of dividend equivalents as an income tax expense or benefit. See "Note 10 — Income Taxes". The Company follows the guidance for income taxes in recognizing, measuring, presenting and disclosing in its financial statements uncertain tax positions taken or expected to be taken on its income tax returns. Income tax expense is based on pre-tax accounting income, including adjustments made for the recognition or derecognition related to uncertain tax positions. The recognition or derecognition of income tax expense related to uncertain tax positions is determined under the guidance, and the Company's policy is to treat interest and penalties related to uncertain tax positions as part of pre-tax income. Deferred tax assets and liabilities are recognized for the future tax attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in earnings in the period of change. Management applies the “more-likely-than-not criteria” when determining tax benefits. Foreign Currency Translation Assets and liabilities denominated in foreign currencies have been translated at rates of exchange prevailing at the end of the periods presented in accordance with the accounting guidance for foreign currency translation. Revenues and expenses transacted in foreign currency have been translated at average monthly exchange rates during the period. Translation gains and losses are included in the foreign currency translation adjustment, which is included as a component of other comprehensive income (loss) in the condensed consolidated statements of changes in stockholders' equity. Foreign currency transaction gains and losses are included in the condensed consolidated statements of income. Financial Instruments and Fair Value The Company accounts for financial instruments measured at fair value in accordance with accounting guidance for fair value measurements and disclosures which establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy under the pronouncement are described below: Basis of Fair Value Measurement Level 1 – Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; Level 2 – Quoted prices in markets that are not active or financial instruments for which all significant inputs are observable, either directly or indirectly; and Level 3 – Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. In determining the appropriate levels, the Company performs an analysis of the assets and liabilities that are subject to these disclosures. At each reporting period, all assets and liabilities for which the fair value measurement is based on significant unobservable inputs or instruments which trade infrequently and therefore have little or no price transparency are classified as Level 3. Transfers between levels are recognized as of the end of the period in which they occur. See "Note 5 — Fair Value of Financial Instruments". Fair Value of Other Financial Instruments The Company believes that the carrying values of all other financial instruments presented in the condensed consolidated statements of financial condition approximate their fair value generally due to their short-term nature and generally negligible credit risk. These fair value measurements would be categorized as Level 2 within the fair value hierarchy. Property and Equipment Property and equipment is stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the life of the assets. Amortization of leasehold improvements is computed using the straight-line method over the lesser of the life of the asset or the remaining term of the lease. Estimated useful lives of the Company’s fixed assets are generally as follows: Aircraft – 7 years Equipment – 5 years Furniture and fixtures – 7 years Leasehold improvements – the lesser of 10 years or the remaining lease term Business Information The Company's activities as an investment banking firm constitute a single business segment, with substantially all revenues generated from advisory services, which includes engagements relating to mergers and acquisitions, financing advisory and restructuring, and capital advisory services. The Company earns less than 1% of its revenues from interest income and investment gains (losses) on investments. Recently Adopted Accounting Pronouncements In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting ("ASU 2016-09"). ASU 2016-09 amends the guidance in former ASC Topic 718, Compensation – Stock Compensation. The standard is effective for public entities for annual reporting periods beginning after December 15, 2016 and the Company adopted these amendments effective on January 1, 2017. The impact of ASU No. 2016-09 resulted in a net increase to the provision for income taxes during the nine month period ending September 30, 2017 related to excess tax benefits and tax deficiencies for its restricted stock unit compensation, which under the prior standard was recorded as an adjustment to retained earnings. See "Note 10 — Income Taxes". Accounting Developments In May 2014, the FASB issued ASU 2014-9 "Revenue from Contracts with Customers" codifying ASC 606, Revenue Recognition - Revenue from Contracts with Customers, which amends the guidance in former ASC 605, Revenue Recognition. The standard is effective for public entities for annual reporting periods beginning after December 15, 2017 and the Company will adopt this standard effective on January 1, 2018. The Company has been evaluating the impact of the future adoption of ASU 2014-09 on our consolidated financial statements which requires applying the new standard to prior comparative periods when reporting under the new standard becomes effective. Based on the current guidance provided by the AICPA industry task force on Broker-Dealers, the AICPA's Revenue Recognition Working Group and the AICPA's Financial Reporting Executive Committee (FinREC), the Company expects certain revenue, which is currently recognized at the time the services are provided, will be recognized over the term of the engagement. The Company will also change the current presentation of certain reimbursed costs from a net presentation to a gross basis. In February 2016, the FASB issued ASU No. 2016-02, Leases ("ASU 2016-02"). ASU 2016-02 amends the guidance in former ASC 840, Leases. Management is currently evaluating the impact of the future adoption of ASU 2016-02 on the Company’s consolidated financial statements. The standard is effective for public entities for annual reporting periods beginning after December 15, 2018 and the Company will adopt these amendments effective on January 1, 2019.

Cash and Cash Equivalents

Cash and Cash Equivalents	9 Months Ended
	Sep. 30, 2017
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	Cash and Cash Equivalents The carrying values of the Company's cash and cash equivalents are as follows: As of September 30, As of December 31, 2017 2016 (in thousands) (unaudited) Cash $ 37,548 $ 85,047 Cash equivalents 8,832 9,013 Restricted cash - letters of credit 4,495 4,253 Total cash and cash equivalents $ 50,875 $ 98,313 The carrying value of the Company's cash equivalents approximates fair value. Letters of credit are secured by cash held on deposit.

Other Assets

Other Assets	9 Months Ended
	Sep. 30, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other Assets	Other Assets Other assets consist of the following: As of September 30, As of December 31, 2017 2016 (in thousands) (unaudited) Prepaid expenses $ 3,590 $ 4,295 Investments in merchant banking funds 1,202 1,689 Rent deposits 1,771 1,517 Other tangible assets 1,235 540 Intangible assets 100 300 Total other assets $ 7,898 $ 8,341 At September 30, 2017 and December 31, 2016 , the Company had an investment in a previously sponsored merchant banking fund, Greenhill Capital Partners II (“GCP II”), and an interest in Barrow Street III, a real estate investment fund. At September 30, 2017 , the Company had no remaining unfunded commitments.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Fair Value of Financial Instruments There were no Level 1 or Level 2 assets or liabilities measured in the fair value hierarchy during the three and nine month periods ended September 30, 2017 and 2016 . There were no Level 3 assets measured at fair value during the three and nine month periods ended September 30, 2017 and 2016 . In connection with the acquisition of Cogent Partners, LP and its affiliates ("Cogent") (now known as the secondary advisory business), the Company agreed to pay to the sellers in the future $18.9 million in cash and 334,048 shares of Greenhill common stock if certain agreed revenue targets are achieved (the "Earnout"). The cash payment and the issuance of common shares related to the Earnout will be made if secondary capital advisory revenues of $80.0 million or more are earned during either the two year period ending on the second anniversary of the closing or the two year period ending on the fourth anniversary of the closing. The revenue generated by the secondary fund placement business for the first two year period ended March 31, 2017 was slightly less than required to achieve the Cogent earnout. If the revenue target is achieved during the second two period ending on March 31, 2019, the contingent consideration will be paid promptly after that date. If the revenue target is not achieved during the remaining two year earnout period, a payment will not be made. The fair value of the contingent cash consideration was valued on the date of the acquisition at $13.1 million and is remeasured quarterly based on a probability weighted present value discount that the revenue target may be achieved. At September 30, 2017 , based on changes in the estimated probability of achievement and the present value of the remaining term, the contingent cash consideration was valued at $ 9.6 million . For the three and nine month periods ended September 30, 2017 , the Company recognized an increase in other operating expenses of $1.9 million and a decrease in other operating expenses of $5.6 million , respectively. For the three and nine month periods ended September 30, 2016 , the Company recognized increases in other operating expenses of $0.03 million and $ 1.4 million , respectively. See "Note 9 — Earnings per Share". The following table sets forth the measurement at fair value on a recurring basis of the contingent cash consideration due the selling unitholders of Cogent related to the Earnout. The liability arose as a result of the acquisition of Cogent and is categorized as a Level 3 liability, which is remeasured each quarterly period based on the probability of achieving the target revenue threshold and weighted average discount rate as discussed below. Liabilities Measured at Fair Value on a Recurring Basis as of September 30, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance as of September 30, 2017 (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ — $ — $ 9,456 $ 9,456 Total $ — $ — $ 9,456 $ 9,456 Liabilities Measured at Fair Value on a Recurring Basis as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance as of December 31, 2016 (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ — $ — $ 15,095 $ 15,095 Total $ — $ — $ 15,095 $ 15,095 Changes in Level 3 liabilities measured at fair value on a recurring basis for the three and nine month periods ended September 30, 2017 are as follows: Opening Balance as of July 1, 2017 Total realized and unrealized gains (losses) included in Net Income Unrealized gains (losses) included in Other Comprehensive Income Purchases Issues Sales Settlements Closing Balance as of September 30, 2017 Unrealized gains (losses) for Level 3 liabilities outstanding at September 30, 2017 (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ 7,582 $ (1,874 ) $ — $ — $ — $ — $ — $ 9,456 $ (1,874 ) Total $ 7,582 $ (1,874 ) $ — $ — $ — $ — $ — $ 9,456 $ (1,874 ) Opening Balance as of January 1, 2017 Total realized and unrealized gains (losses) included in Net Income Unrealized gains (losses) included in Other Comprehensive Income Purchases Issues Sales Settlements Closing Balance as of September 30, 2017 Unrealized gains (losses) for Level 3 liabilities outstanding at September 30, 2017 (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ 15,095 $ 5,639 $ — $ — $ — $ — $ — $ 9,456 $ 5,639 Total $ 15,095 $ 5,639 $ — $ — $ — $ — $ — $ 9,456 $ 5,639 Changes in Level 3 liabilities measured at fair value on a recurring basis for the three and nine month periods ended September 30, 2016 are as follows: Opening Balance as of July 1, 2016 Total realized and unrealized gains (losses) included in Net Income Unrealized gains (losses) included in Other Comprehensive Income Purchases Issues Sales Settlements Closing Balance as of September 30, 2016 Unrealized gains (losses) for Level 3 liabilities outstanding at September 30, 2016 (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ 15,104 $ 35 $ — $ — $ — $ — $ — $ 15,069 $ 35 Total $ 15,104 $ 35 $ — $ — $ — $ — $ — $ 15,069 $ 35 Opening Balance as of January 1, 2016 Total realized and unrealized gains (losses) included in Net Income Unrealized gains (losses) included in Other Comprehensive Income Purchases Issues Sales Settlements Closing Balance as of September 30, 2016 Unrealized gains (losses) for Level 3 liabilities outstanding at September 30, 2016 (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ 13,647 $ (1,422 ) $ — $ — $ — $ — $ — $ 15,069 $ (1,422 ) Total $ 13,647 $ (1,422 ) $ — $ — $ — $ — $ — $ 15,069 $ (1,422 ) Realized and unrealized gains (losses) are reported as a component of other operating expenses in the condensed consolidated statements of income. The following table presents quantitative information about the significant unobservable inputs utilized by the Company in the fair value measure of Level 3 liabilities measured at fair value on a recurring basis, as of September 30, 2017 : Fair Value as of September 30, 2017 Valuation Technique(s) Unobservable Input(s) Range (Weighted Average) (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ 9,456 Present value of expected payments Discount rate 13 % Forecast revenue (a) _____________________________________________ (a) The Company's estimate of contingent consideration as of September 30, 2017 was principally based on the acquired business' (i) actual revenue generation from April 1, 2015 through March 31, 2017 and (ii) actual and projected revenue generation from April 1, 2017 through March 31, 2019. Valuation Processes - Level 3 Measurements - The Company utilizes a valuation technique based on a present value method applied to the probability of achieving a range of potential revenue outcomes. The valuation was conducted by the Company. The Company updates unobservable inputs each reporting period and has a formal process in place to review changes in fair value. Sensitivity Analysis - Level 3 Measurements - The significant unobservable inputs used in determining fair value are the discount rate and forecast revenue information. Significant increases (decreases) in the discount rate would have resulted in a lower (higher) fair value measurement. Significant increases (decreases) in the forecast revenue information would result in a higher (lower) fair value measurement. For all significant unobservable inputs used in the fair value measurement of the Level 3 liabilities, a change in one of the inputs would not necessarily result in a directionally similar change in the other inputs.

Related Parties

Related Parties	9 Months Ended
	Sep. 30, 2017
Related Party Transactions [Abstract]
Related Parties	Related Parties At September 30, 2017 and December 31, 2016 , the Company had no amounts receivable or payable to related parties. The Company subleases airplane and office space to a firm owned by the Chairman of the Company. The Company recognized rent reimbursements of $0.02 million and for each of the three month periods ended September 30, 2017 and 2016 , respectively, and $0.06 million and $0.05 million for the nine month periods ended September 30, 2017 and 2016 , respectively, which are included as a reduction of occupancy and equipment rental on the condensed consolidated statements of income. On September 25, 2017, the Company's Chairman, through an entity controlled by him, and the Company's Chief Executive Officer, in his personal capacity and through an entity controlled by him, each entered into a Subscription Agreement for the purchase of $10.0 million , for an aggregate total of $20.0 million , of the Company's common stock at the final price per share of the Company’s recently completed tender offer. The funding of the purchases by the Chairman and Chief Executive Officer occurred on November 9, 2017, the 11th trading day following the expiration date of the tender offer, and a total of 1,159,420 common shares were issued. See "Note 8 — Equity" and "Note 12 — Subsequent Events".

Bank Loan Facilities

Bank Loan Facilities	9 Months Ended
	Sep. 30, 2017
Debt Disclosure [Abstract]
Bank Loan Facilities	Bank Loan Facilities At September 30, 2017 , the Company had a $90.0 million revolving bank loan facility to provide for working capital needs and for other general corporate purposes. During 2017, the borrowing capacity under the revolving loan facility was increased by $20.0 million to $90.0 million . The maturity date of the revolving loan facility was April 30, 2018. Interest on the borrowings was based on the higher of 3.50% or the U.S. Prime Rate ( 4.25% at September 30, 2017) and was payable monthly. The weighted average daily borrowings outstanding under the revolving bank loan facility were approximately $64.8 million and $52.2 million for the nine months ended September 30, 2017 and 2016 , respectively. The weighted average interest rate related to the bank loan facility was 4.04% and 3.50% for the nine months ended September 30, 2017 and 2016 , respectively. In connection with the acquisition of Cogent in April 2015, the Company borrowed $45.0 million , which was comprised of two bank term loan facilities (the "Term Loan Facilities"), each in an original principal amount of $22.5 million . One Term Loan Facility was paid in full in advance of its maturity date in April 2016. The other Term Loan Facility had a maturity date of April 30, 2018 (the " Three Year Facility"), was payable in four equal semi-annual installments beginning on October 31, 2016 and bore interest at the Prime Rate plus one and one-quarter percent ( 1.25% ) per annum, which interest rate was to be reduced to the Prime Rate plus three-quarters of one percent ( 0.75% ) per annum when the amount outstanding on the Three Year Facility was $7.5 million or less. During 2017, the Company repaid the outstanding balance of the term loan of $16.9 million , including $11.3 million in the third quarter, in full satisfaction of the remaining tranche of the term loan facility used to fund the acquisition of Cogent. There were no prepayment penalties for the early repayment of the Term Loan Facilities and principal amounts repaid cannot be reborrowed. The interest rate applicable to the Term Loan Facilities can never be less than four percent ( 4.00% ) per annum. The weighted average interest rate related to the Term Loan Facilities was 5.17% and 4.67% for the nine months ended September 30, 2017 and 2016 , respectively. The bank loan facilities were provided by a U.S. banking institution and secured by any cash distributed in respect of the Company’s investment in the U.S. based merchant banking funds and cash distributions from G&Co, CP LP and GCI and advisory fees receivable from G&Co. In addition, the bank loan facilities had a prohibition on the incurrence of additional indebtedness without the prior approval of the lenders and the Company was required to comply with certain financial and liquidity covenants. At September 30, 2017 , the Company was compliant with all bank loan covenants. On September 25, 2017, the Company announced plans for a leveraged recapitalization, which included plans to borrow $300 million of term loans, which was subsequently increased to $350 million , and to use the net proceeds to repay the amount outstanding under the existing bank loan facilities and repurchase up to $235 million of the Company's common stock, which was subsequently increased to $285 million of the Company's common stock. In accordance with these plans, the Company elected to repay in full all amounts outstanding and terminate its commitments under the Three Year Facility on September 29, 2017 with the proceeds from a drawing on its revolving bank loan facility. See "Note 12 — Subsequent Events".

Equity

Equity	9 Months Ended
	Sep. 30, 2017
Stockholders' Equity Note [Abstract]
Equity	Equity On September 27, 2017, a dividend of $0.45 per share was paid to stockholders of record on September 13, 2017. For the nine months ended September 30, 2017 , dividend payments of $1.35 per share were paid to stockholders. Dividends include dividend equivalents of $6.2 million and $6.4 million , which were paid on outstanding restricted stock units for the nine months ended September 30, 2017 and 2016 , respectively. During the nine months ended September 30, 2017 , 1,095,224 restricted stock units vested and were settled in shares of common stock of which the Company is deemed to have repurchased 448,738 shares at an average price of $29.06 per share in conjunction with the payment of tax liabilities in respect of stock delivered to its employees in settlement of restricted stock units. During the nine months ended September 30, 2016 , 850,387 restricted stock units vested and were settled in shares of common stock of which the Company is deemed to have repurchased 319,194 shares at an average price of $25.10 per share in conjunction with the payment of tax liabilities in respect of stock delivered to its employees in settlement of restricted stock units. In addition, during the nine months ended September 30, 2016 , the Company repurchased in open market transactions 626,455 shares of its common stock at an average price of $20.22 per share. On September 25, 2017, the Company announced that its Board of Directors had authorized the repurchase of up to $285 million of the Company's common stock and approved a cash tender offer for up to 9,000,000 shares of the Company's common stock at a purchase price of $17.00 per share, which was subsequently increased to up to 12,000,000 shares of the Company's common stock at a purchase price of $17.25 per share. Prior to the public announcement of the tender offer, the Company's Chairman, through an entity controlled by him, and the Company's Chief Executive Officer, in his personal capacity and through an entity controlled by him, each entered into a Subscription Agreement for the purchase of $10.0 million , for an aggregate total of $20.0 million , of the Company's common stock at the final tender offer price per share. The funding of the purchases by the Chairman and Chief Executive Officer occurred on November 9, 2017, the 11th trading day following the expiration date of the tender offer, and a total of 1,159,420 common shares were issued. Under the requirements of ASC 505, these purchases were included in subscription receivable on the condensed consolidated statement of financial condition. See "Note 6 — Related Parties" and "Note 12 — Subsequent Events".

Earnings per Share

Earnings per Share	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Earnings per Share	Earnings per Share The computations of basic and diluted EPS are set forth below: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2017 2016 2017 2016 (in thousands, except per share amounts, unaudited) Numerator for basic and diluted EPS — net income (loss) allocated to common stockholders $ (5,912 ) $ 13,110 $ (413 ) $ 37,095 Denominator for basic EPS — weighted average number of shares 32,281 31,686 32,371 31,954 Add — dilutive effect of: Weighted average number of incremental shares issuable from restricted stock units — (1) 7 — (2) 7 Denominator for diluted EPS — weighted average number of shares and dilutive potential shares 32,281 31,693 32,371 31,961 Earnings (loss) per share: Basic $ (0.18 ) $ 0.41 $ (0.01 ) $ 1.16 Diluted $ (0.18 ) $ 0.41 $ (0.01 ) $ 1.16 The weighted number of shares and dilutive potential shares do not include 334,048 shares of common stock, which will be issued to certain selling unitholders of Cogent, following the fourth anniversary of the acquisition if the revenue target related to the Earnout is achieved. In the event that the revenue target is achieved, such shares will be included in the Company’s share count at March 31, 2019. If the revenue target is not achieved such shares of common stock will not be issued. See "Note 5 — Fair Value of Financial Instruments". ________________________ (1) Excludes 256 shares for the three month period ended September 30, 2017 , which were considered antidilutive and thus were not included in the above calculation. (2) Excludes 35,877 shares for the nine month period ended September 30, 2017 , which were considered antidilutive and thus were not included in the above calculation.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Income Taxes The Company's effective tax rate varies depending on the jurisdiction in which the income is earned. Certain foreign sourced income is taxed at a lower effective rate than U.S. income. Under the requirements of ASC 740, the Company intends to indefinitely reinvest its non-U.S. subsidiaries earnings outside the United States and does not provide for residual U.S. tax on these earnings. The provision for income taxes for the nine months ending September 30, 2017 reflects a net charge of $1.1 million related to excess tax benefits and tax deficiencies for its restricted stock unit compensation as required by new accounting guidance for share-based compensation effective January 1, 2017 . The Company's condensed consolidated statements of income for periods prior to January 1, 2017 record these excess tax benefits and tax deficiencies as a charge or benefit to stockholders' equity. The Company believes it is more likely than not that the deferred tax asset, which relates principally to compensation expense deducted for book purposes but not yet deducted for tax purposes, will be realized as offsets to: (i) the realization of its deferred tax liabilities and (ii) future taxable income. Any gain or loss resulting from the translation of deferred taxes for foreign affiliates is included in the foreign currency translation adjustment incorporated as a component of other comprehensive income, net of tax, in the condensed consolidated statements of changes in stockholders' equity and the condensed consolidated statements of comprehensive income. The Company's income tax returns are routinely examined by the U.S. federal, U.S. state, and international tax authorities. The Company regularly assesses its tax positions with respect to applicable income tax issues for open tax years in each respective jurisdiction in which the Company operates. As of September 30, 2017 , the Company does not believe the resolution of any current ongoing income tax examinations will have a material adverse impact on the financial position of the Company.

Regulatory Requirements

Regulatory Requirements	9 Months Ended
	Sep. 30, 2017
Regulatory Capital Requirements [Abstract]
Regulatory Requirements	Regulatory Requirements Certain subsidiaries of the Company are subject to various regulatory requirements in the United States, United Kingdom, Australia and certain other jurisdictions, which specify, among other requirements, minimum net capital requirements for registered broker-dealers. G&Co is subject to the SEC’s Uniform Net Capital requirements under Rule 15c3-1 (the “Rule”), which specifies, among other requirements, minimum net capital requirements for registered broker-dealers. The Rule requires G&Co to maintain a minimum net capital of the greater of $5,000 or 1/15 of aggregate indebtedness, as defined in the Rule. As of September 30, 2017 , G&Co’s net capital was $5.2 million , which exceeded its requirement by $4.6 million . G&Co’s aggregate indebtedness to net capital ratio was 1.6 to 1 at September 30, 2017 . Certain distributions and other capital withdrawals of G&Co are subject to certain notifications and restrictive provisions of the Rule. GCI is subject to capital requirements of the FCA. Greenhill Australia is subject to capital requirements of the ASIC. GC LP is subject to capital requirements of the SEC and the FCA. We are also subject to certain regulatory capital requirements in other jurisdictions. As of September 30, 2017 , GCI, Greenhill Australia, GC LP and our other regulated operations were in compliance with local capital adequacy requirements.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2017
Subsequent Events [Abstract]
Subsequent Events	Subsequent Events The Company evaluates subsequent events through the date on which the financial statements are issued. On October 10, 2017, the Company announced that it had increased the planned share repurchases to up to $285 million of the Company's common stock and increased the size and price of its ongoing cash tender offer, commenced on September 27, 2017, to up to 12 million shares of the Company's common stock at $17.25 per share. On October 12, 2017, in connection with a recapitalization plan, the Company entered into a new credit agreement with a syndicate of lenders, who lent $350.0 million under a five -year secured term loan facility and provided a three -year secured revolving credit facility for $20.0 million , which was undrawn at closing. Borrowings under the new credit facilities bear interest at either a base rate plus 2.75% or LIBOR plus 3.75% . The term loan requires quarterly principal amortization payments commencing on March 31, 2018 of $4.375 million through September 30, 2018 and $8.75 million (or $35.0 million annually) beginning December 31, 2018 through September 30, 2022 with the remaining balance of the term loan due at maturity on October 12, 2022. In addition, beginning for the year ended December 31, 2018, the Company is required to make annual prepayments of principal on the term loan of 50% of its annual excess cash flow as defined in the credit agreement. The Company is also required to repay certain amounts of the term loan in connection with the non-ordinary course sale of assets, receipt of insurance proceeds, and the issuance of debt obligations, subject to certain exceptions. All mandatory prepayments of the term loan facility will be applied without penalty or premium. Voluntary prepayments of borrowings under the term loan facility will be permitted. In the event that all or any portion of the term loan facility is prepaid or refinanced or repriced through any amendment prior to April 12, 2019, such repayment, prepayment, refinancing, or repricing will be at 101.0% of the principal amount so repaid, prepaid, refinanced or repriced. The new term and revolving loan facilities are guaranteed by the Company's existing and subsequently acquired or organized wholly-owned U.S. restricted subsidiaries (excluding any registered broker-dealers) and secured with a first priority perfected security interest in certain domestic assets and 100% of the capital stock of each U.S. subsidiary and 65% of the capital stock of each non-U.S. subsidiary, subject to certain exclusions which, for the avoidance of doubt, such security interest shall not include any assets of regulated subsidiaries that are not permitted to be pledged by law, statute or regulation, including cash held by regulated subsidiaries and any other capital required to meet and maintain regulatory capital requirements. The credit facilities contain certain covenants that limit the Company's ability above certain permitted amounts to incur additional indebtedness, make certain acquisitions, pay dividends and repurchase shares. The term loan facility does not have financial covenants and the revolving loan facility is subject to a springing total net leverage ratio financial covenant, subject to certain step downs, if the Company's borrowings under the revolving loan facility exceed $12.5 million . The Company is also subject to certain other non-financial covenants. On October 12, 2017, in connection with entry into the new credit agreement, the Company repaid in full all amounts outstanding and terminated its commitments under its preexisting revolving bank loan facility with the net proceeds from the new term loan facility. On October 18, 2017 , the Board of Directors of the Company declared a quarterly dividend of $0.05 per share. The dividend will be payable on December 20, 2017 to the common stockholders of record on December 6, 2017 . On October 25, 2017, the Company's tender offer expired, and, on October 30, 2017, the Company announced that it had accepted for purchase 3,434,137 shares of its common stock at the purchase price of $17.25 per share for a total cash cost of approximately $59.2 million, excluding fees and expenses relating to the tender offer. On November 9, 2017, the Company's Chairman, through an entity controlled by him, and the Company's Chief Executive Officer, in his personal capacity and through an entity controlled by him, each purchased of $10.0 million of the Company's common stock, for an aggregate total of $20.0 million , and a total of 1,159,420 common shares were issued. See "Note 6 — Related Parties" and "Note 8 — Equity".

Summary of Significant Accoun21

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2017
Accounting Policies [Abstract]
Basis of Financial Information	Basis of Financial Information These condensed consolidated financial statements are prepared in conformity with accounting principles generally accepted in the United States (U.S. GAAP), which require management to make estimates and assumptions regarding future events that affect the amounts reported in our financial statements and these footnotes, including investment valuations, compensation accruals and other matters. Management believes that the estimates used in preparing its condensed consolidated financial statements are reasonable and prudent. Actual results could differ materially from those estimates. Certain reclassifications have been made to prior year information to conform to current year presentation. The condensed consolidated financial statements of the Company include all consolidated accounts of Greenhill & Co., Inc. and all other entities in which the Company has a controlling interest after eliminations of all significant inter-company accounts and transactions. These condensed consolidated financial statements are unaudited and should be read in conjunction with the audited consolidated financial statements and notes thereto for the year ended December 31, 2016 included in the Company's Annual Report on Form 10-K filed with the SEC. The condensed consolidated financial information as of December 31, 2016 has been derived from audited consolidated financial statements not included herein. The results of operations for interim periods are not necessarily indicative of results for the entire year.
Revenue Recognition	Revenue Recognition Advisory Revenues It is the Company's accounting policy to recognize revenue when (i) there is persuasive evidence of an arrangement with a client, (ii) the agreed-upon services have been completed and delivered to the client or the transaction or events noted in the engagement letter are determined to be substantially complete, (iii) fees are fixed and determinable, and (iv) collection is reasonably assured. The Company recognizes advisory fee revenues for mergers and acquisitions or financing advisory and restructuring engagements when the services related to the underlying transactions are completed in accordance with the terms of the engagement letter and all other requirements for revenue recognition are satisfied. The Company recognizes capital advisory fees from primary capital raising transactions at the time of the client's acceptance of capital or capital commitments to a fund in accordance with the terms of the engagement letter. Generally, fee revenue is determined based upon a fixed percentage of capital committed to the fund. For multiple closings, revenue is recognized at each interim closing based on the amount of capital committed at each closing at the fixed fee percentage. At the final closing, revenue is recognized at the fixed percentage for the amount of capital committed since the last interim closing. The Company recognizes capital advisory fees from secondary market transactions at the time the sale or transfer of the capital interest is completed in accordance with the terms of the engagement letter. Generally, fee revenue is determined based upon a fixed percentage of the transaction value. While the majority of the Company's fee revenue is earned at the conclusion of a transaction or closing of a fund, on-going retainer fees, substantially all of which relate to non-success based strategic advisory and financing advisory and restructuring assignments, are also earned and recognized as advisory fee revenue over the period in which the related service is rendered. The Company’s clients reimburse certain expenses incurred by the Company in the conduct of advisory engagements. Expenses are reported net of such client reimbursements. Client reimbursements totaled $1.0 million and $1.4 million for the three months ended September 30, 2017 and 2016 , respectively, and $3.0 million and $4.6 million for the nine months ended September 30, 2017 and 2016 , respectively. Investment Revenues Investment revenues consist of gains (or losses) on the Company's investments in certain merchant banking funds and interest income. The Company recognizes revenue on its investments in merchant banking funds based on its allocable share of realized and unrealized gains (or losses) reported by such funds.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company’s cash and cash equivalents consist of (i) cash held on deposit with financial institutions, (ii) cash equivalents and (iii) restricted cash. The Company maintains its cash and cash equivalents with financial institutions with high credit ratings. The Company considers all highly liquid investments with a maturity date of three months or less, when purchased, to be cash equivalents. Cash equivalents primarily consist of money market funds and overnight deposits. Management believes that the Company is not exposed to significant credit risk due to the financial position of the depository institutions in which those deposits are held. See "Note 3 — Cash and Cash Equivalents".
Advisory Fees Receivables	Advisory Fees Receivables Receivables are stated net of an allowance for doubtful accounts. The estimate for the allowance for doubtful accounts is derived by the Company by utilizing past client transaction history and an assessment of the client’s creditworthiness. The Company recorded bad debt expense of $0.3 million and $1.1 million for the three and nine month periods ended September 30, 2017 , respectively. The Company recorded bad debt expense of $0.0 million and $0.4 million for the three and nine month periods ended September 30, 2016 , respectively. Included in the advisory fees receivable balance at September 30, 2017 and December 31, 2016 were $28.5 million and $26.1 million , respectively, of long term receivables related to primary capital advisory engagements which are generally paid in installments over a period of three years . Included as a component of investment revenues on the condensed consolidated statements of income is interest income related to primary capital advisory engagements of $0.2 million and $0.1 million for the three month periods ended September 30, 2017 and 2016 , respectively, and $0.5 million and $0.6 million for the nine month periods ended September 30, 2017 and 2016 , respectively. Credit risk related to advisory fees receivable is disbursed across a large number of clients located in various geographic areas. The Company controls credit risk through credit approvals and monitoring procedures but does not require collateral to support accounts receivable.
Goodwill	Goodwill Goodwill is the cost in excess of the fair value of identifiable net assets at acquisition date. The Company tests its goodwill for impairment at least annually. An impairment loss is triggered if the estimated fair value of an operating unit is less than estimated net book value. Such loss is calculated as the difference between the estimated fair value of goodwill and its carrying value. Goodwill is translated at the rate of exchange prevailing at the end of the periods presented in accordance with the accounting guidance for foreign currency translation. Any translation gain or loss is included in the foreign currency translation adjustment, which is included as a component of other comprehensive income in the condensed consolidated statements of changes in stockholders' equity.
Other Assets	Other Assets Included in other assets are the Company's investments in merchant banking funds, which are recorded under the equity method of accounting, based upon the Company's proportionate share of the estimated fair value of the underlying merchant banking fund's net assets. The value of merchant banking fund investments is determined by management of the fund after giving consideration to the cost of the security, quoted market prices, the pricing of other sales of securities by the portfolio company, the price of securities of other companies comparable to the portfolio company, purchase multiples paid in other comparable third-party transactions, the original purchase price multiple, market conditions, liquidity, operating results and other qualitative and quantitative factors. The funds may apply discounts to reflect the lack of liquidity and other transfer restrictions.
Restricted Stock Units	Restricted Stock Units The Company accounts for its share-based compensation payments by recording the fair value of restricted stock units granted to employees as compensation expense. The restricted stock units are generally amortized over a four to five -year service period following the date of grant. Compensation expense is determined based upon the fair market value of the Company’s common stock at the date of grant. As the Company expenses the awards, the restricted stock units recognized are recorded within stockholders' equity. The restricted stock units are reclassified into common stock and additional paid-in capital upon vesting. The Company records as treasury stock the repurchase of stock delivered to its employees in settlement of tax liabilities incurred upon the vesting of restricted stock units. The Company records dividend equivalent payments on outstanding restricted stock units as a dividend payment and a charge to stockholders' equity.
Earnings per Share	Earnings per Share The Company calculates basic earnings per share (“EPS”) by dividing net income allocated to common stockholders by the sum of (i) the weighted average number of shares outstanding for the period and (ii) the weighted average number of shares deemed issuable due to the vesting of restricted stock units for accounting purposes. See "Note 8 — Equity". The Company calculates diluted EPS by dividing net income allocated to common stockholders by the sum of (i) basic shares per above and (ii) the dilutive effect of the common stock deliverable pursuant to restricted stock units for which future service is required. Under the treasury method, the number of shares issuable upon the vesting of restricted stock units included in the calculation of diluted EPS is the excess, if any, of the number of shares expected to be issued, less the number of shares that could be purchased by the Company with the proceeds to be received upon settlement at the average market closing price during the reporting period. See "Note 9 — Earnings per Share".
Provision for Taxes	Provision for Taxes The Company accounts for taxes in accordance with the accounting guidance for income taxes which requires the recognition of tax benefits or expenses on the temporary differences between the financial reporting and tax bases of its assets and liabilities. Additionally, the Company accounts for the net tax (cost) from the delivery of restricted stock units and payment of dividend equivalents as an income tax expense or benefit. See "Note 10 — Income Taxes". The Company follows the guidance for income taxes in recognizing, measuring, presenting and disclosing in its financial statements uncertain tax positions taken or expected to be taken on its income tax returns. Income tax expense is based on pre-tax accounting income, including adjustments made for the recognition or derecognition related to uncertain tax positions. The recognition or derecognition of income tax expense related to uncertain tax positions is determined under the guidance, and the Company's policy is to treat interest and penalties related to uncertain tax positions as part of pre-tax income. Deferred tax assets and liabilities are recognized for the future tax attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to be recovered or settled. The effect on deferred tax assets and liabilities of a change in tax rates is recognized in earnings in the period of change. Management applies the “more-likely-than-not criteria” when determining tax benefits.
Foreign Currency Translation	Foreign Currency Translation Assets and liabilities denominated in foreign currencies have been translated at rates of exchange prevailing at the end of the periods presented in accordance with the accounting guidance for foreign currency translation. Revenues and expenses transacted in foreign currency have been translated at average monthly exchange rates during the period. Translation gains and losses are included in the foreign currency translation adjustment, which is included as a component of other comprehensive income (loss) in the condensed consolidated statements of changes in stockholders' equity. Foreign currency transaction gains and losses are included in the condensed consolidated statements of income.
Financial Instruments and Fair Value	Financial Instruments and Fair Value The Company accounts for financial instruments measured at fair value in accordance with accounting guidance for fair value measurements and disclosures which establishes a fair value hierarchy that prioritizes the inputs to valuation techniques used to measure fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). The three levels of the fair value hierarchy under the pronouncement are described below: Basis of Fair Value Measurement Level 1 – Unadjusted quoted prices in active markets that are accessible at the measurement date for identical, unrestricted assets or liabilities; Level 2 – Quoted prices in markets that are not active or financial instruments for which all significant inputs are observable, either directly or indirectly; and Level 3 – Prices or valuations that require inputs that are both significant to the fair value measurement and unobservable. A financial instrument’s level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. In determining the appropriate levels, the Company performs an analysis of the assets and liabilities that are subject to these disclosures. At each reporting period, all assets and liabilities for which the fair value measurement is based on significant unobservable inputs or instruments which trade infrequently and therefore have little or no price transparency are classified as Level 3. Transfers between levels are recognized as of the end of the period in which they occur. See "Note 5 — Fair Value of Financial Instruments". Fair Value of Other Financial Instruments The Company believes that the carrying values of all other financial instruments presented in the condensed consolidated statements of financial condition approximate their fair value generally due to their short-term nature and generally negligible credit risk. These fair value measurements would be categorized as Level 2 within the fair value hierarchy.
Property and Equipment	Property and Equipment Property and equipment is stated at cost less accumulated depreciation and amortization. Depreciation is computed using the straight-line method over the life of the assets. Amortization of leasehold improvements is computed using the straight-line method over the lesser of the life of the asset or the remaining term of the lease. Estimated useful lives of the Company’s fixed assets are generally as follows: Aircraft – 7 years Equipment – 5 years Furniture and fixtures – 7 years Leasehold improvements – the lesser of 10 years or the remaining lease term
Business Information	Business Information The Company's activities as an investment banking firm constitute a single business segment, with substantially all revenues generated from advisory services, which includes engagements relating to mergers and acquisitions, financing advisory and restructuring, and capital advisory services. The Company earns less than 1% of its revenues from interest income and investment gains (losses) on investments.
Recently Adopted Accounting Pronouncements and Accounting Developments	Recently Adopted Accounting Pronouncements In March 2016, the FASB issued ASU No. 2016-09, Improvements to Employee Share-Based Payment Accounting ("ASU 2016-09"). ASU 2016-09 amends the guidance in former ASC Topic 718, Compensation – Stock Compensation. The standard is effective for public entities for annual reporting periods beginning after December 15, 2016 and the Company adopted these amendments effective on January 1, 2017. The impact of ASU No. 2016-09 resulted in a net increase to the provision for income taxes during the nine month period ending September 30, 2017 related to excess tax benefits and tax deficiencies for its restricted stock unit compensation, which under the prior standard was recorded as an adjustment to retained earnings. See "Note 10 — Income Taxes". Accounting Developments In May 2014, the FASB issued ASU 2014-9 "Revenue from Contracts with Customers" codifying ASC 606, Revenue Recognition - Revenue from Contracts with Customers, which amends the guidance in former ASC 605, Revenue Recognition. The standard is effective for public entities for annual reporting periods beginning after December 15, 2017 and the Company will adopt this standard effective on January 1, 2018. The Company has been evaluating the impact of the future adoption of ASU 2014-09 on our consolidated financial statements which requires applying the new standard to prior comparative periods when reporting under the new standard becomes effective. Based on the current guidance provided by the AICPA industry task force on Broker-Dealers, the AICPA's Revenue Recognition Working Group and the AICPA's Financial Reporting Executive Committee (FinREC), the Company expects certain revenue, which is currently recognized at the time the services are provided, will be recognized over the term of the engagement. The Company will also change the current presentation of certain reimbursed costs from a net presentation to a gross basis. In February 2016, the FASB issued ASU No. 2016-02, Leases ("ASU 2016-02"). ASU 2016-02 amends the guidance in former ASC 840, Leases. Management is currently evaluating the impact of the future adoption of ASU 2016-02 on the Company’s consolidated financial statements. The standard is effective for public entities for annual reporting periods beginning after December 15, 2018 and the Company will adopt these amendments effective on January 1, 2019.

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	9 Months Ended
	Sep. 30, 2017
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	The carrying values of the Company's cash and cash equivalents are as follows: As of September 30, As of December 31, 2017 2016 (in thousands) (unaudited) Cash $ 37,548 $ 85,047 Cash equivalents 8,832 9,013 Restricted cash - letters of credit 4,495 4,253 Total cash and cash equivalents $ 50,875 $ 98,313

Other Assets (Tables)

Other Assets (Tables)	9 Months Ended
	Sep. 30, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Carrying Value of Investments in Merchant Banking Funds	Other assets consist of the following: As of September 30, As of December 31, 2017 2016 (in thousands) (unaudited) Prepaid expenses $ 3,590 $ 4,295 Investments in merchant banking funds 1,202 1,689 Rent deposits 1,771 1,517 Other tangible assets 1,235 540 Intangible assets 100 300 Total other assets $ 7,898 $ 8,341

Fair Value of Financial Instr24

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2017
Fair Value Disclosures [Abstract]
Fair Value Measurements, Recurring and Nonrecurring	The following table sets forth the measurement at fair value on a recurring basis of the contingent cash consideration due the selling unitholders of Cogent related to the Earnout. The liability arose as a result of the acquisition of Cogent and is categorized as a Level 3 liability, which is remeasured each quarterly period based on the probability of achieving the target revenue threshold and weighted average discount rate as discussed below. Liabilities Measured at Fair Value on a Recurring Basis as of September 30, 2017 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance as of September 30, 2017 (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ — $ — $ 9,456 $ 9,456 Total $ — $ — $ 9,456 $ 9,456 Liabilities Measured at Fair Value on a Recurring Basis as of December 31, 2016 Quoted Prices in Active Markets for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Balance as of December 31, 2016 (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ — $ — $ 15,095 $ 15,095 Total $ — $ — $ 15,095 $ 15,095
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation	Changes in Level 3 liabilities measured at fair value on a recurring basis for the three and nine month periods ended September 30, 2017 are as follows: Opening Balance as of July 1, 2017 Total realized and unrealized gains (losses) included in Net Income Unrealized gains (losses) included in Other Comprehensive Income Purchases Issues Sales Settlements Closing Balance as of September 30, 2017 Unrealized gains (losses) for Level 3 liabilities outstanding at September 30, 2017 (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ 7,582 $ (1,874 ) $ — $ — $ — $ — $ — $ 9,456 $ (1,874 ) Total $ 7,582 $ (1,874 ) $ — $ — $ — $ — $ — $ 9,456 $ (1,874 ) Opening Balance as of January 1, 2017 Total realized and unrealized gains (losses) included in Net Income Unrealized gains (losses) included in Other Comprehensive Income Purchases Issues Sales Settlements Closing Balance as of September 30, 2017 Unrealized gains (losses) for Level 3 liabilities outstanding at September 30, 2017 (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ 15,095 $ 5,639 $ — $ — $ — $ — $ — $ 9,456 $ 5,639 Total $ 15,095 $ 5,639 $ — $ — $ — $ — $ — $ 9,456 $ 5,639 Changes in Level 3 liabilities measured at fair value on a recurring basis for the three and nine month periods ended September 30, 2016 are as follows: Opening Balance as of July 1, 2016 Total realized and unrealized gains (losses) included in Net Income Unrealized gains (losses) included in Other Comprehensive Income Purchases Issues Sales Settlements Closing Balance as of September 30, 2016 Unrealized gains (losses) for Level 3 liabilities outstanding at September 30, 2016 (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ 15,104 $ 35 $ — $ — $ — $ — $ — $ 15,069 $ 35 Total $ 15,104 $ 35 $ — $ — $ — $ — $ — $ 15,069 $ 35 Opening Balance as of January 1, 2016 Total realized and unrealized gains (losses) included in Net Income Unrealized gains (losses) included in Other Comprehensive Income Purchases Issues Sales Settlements Closing Balance as of September 30, 2016 Unrealized gains (losses) for Level 3 liabilities outstanding at September 30, 2016 (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ 13,647 $ (1,422 ) $ — $ — $ — $ — $ — $ 15,069 $ (1,422 ) Total $ 13,647 $ (1,422 ) $ — $ — $ — $ — $ — $ 15,069 $ (1,422 )
Fair Value Inputs, Liabilities, Quantitative Information	The following table presents quantitative information about the significant unobservable inputs utilized by the Company in the fair value measure of Level 3 liabilities measured at fair value on a recurring basis, as of September 30, 2017 : Fair Value as of September 30, 2017 Valuation Technique(s) Unobservable Input(s) Range (Weighted Average) (in thousands, unaudited) Liabilities Contingent obligation due selling unitholders of Cogent $ 9,456 Present value of expected payments Discount rate 13 % Forecast revenue (a) _____________________________________________ (a) The Company's estimate of contingent consideration as of September 30, 2017 was principally based on the acquired business' (i) actual revenue generation from April 1, 2015 through March 31, 2017 and (ii) actual and projected revenue generation from April 1, 2017 through March 31, 2019.

Earnings per Share (Tables)

Earnings per Share (Tables)	9 Months Ended
	Sep. 30, 2017
Earnings Per Share [Abstract]
Computations of Basic and Diluted Earnings Per Share	The computations of basic and diluted EPS are set forth below: For the Three Months Ended September 30, For the Nine Months Ended September 30, 2017 2016 2017 2016 (in thousands, except per share amounts, unaudited) Numerator for basic and diluted EPS — net income (loss) allocated to common stockholders $ (5,912 ) $ 13,110 $ (413 ) $ 37,095 Denominator for basic EPS — weighted average number of shares 32,281 31,686 32,371 31,954 Add — dilutive effect of: Weighted average number of incremental shares issuable from restricted stock units — (1) 7 — (2) 7 Denominator for diluted EPS — weighted average number of shares and dilutive potential shares 32,281 31,693 32,371 31,961 Earnings (loss) per share: Basic $ (0.18 ) $ 0.41 $ (0.01 ) $ 1.16 Diluted $ (0.18 ) $ 0.41 $ (0.01 ) $ 1.16 The weighted number of shares and dilutive potential shares do not include 334,048 shares of common stock, which will be issued to certain selling unitholders of Cogent, following the fourth anniversary of the acquisition if the revenue target related to the Earnout is achieved. In the event that the revenue target is achieved, such shares will be included in the Company’s share count at March 31, 2019. If the revenue target is not achieved such shares of common stock will not be issued. See "Note 5 — Fair Value of Financial Instruments". ________________________ (1) Excludes 256 shares for the three month period ended September 30, 2017 , which were considered antidilutive and thus were not included in the above calculation. (2) Excludes 35,877 shares for the nine month period ended September 30, 2017 , which were considered antidilutive and thus were not included in the above calculation.

Organization (Details)

Organization (Details)	Sep. 30, 2017state
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of states in which the entity is licensed (state)	50

Summary of Significant Accoun27

Summary of Significant Accounting Policies - Additional Information (Details) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Sep. 30, 2017USD ($)Segment	Sep. 30, 2016USD ($)	Dec. 31, 2016USD ($)
Significant Accounting Policies [Line Items]
Client reimbursements	$ 1	$ 1.4	$ 3	$ 4.6
Bad debt expense	0.3	0	1.1	0.4
Long term receivables related to private equity and real estate capital advisory engagements	28.5		$ 28.5		$ 26.1
Installments period (in years)			3 years
Depreciation and amortization of property and equipment			Depreciation is computed using the straight-line method over the life of the assets. Amortization of leasehold improvements is computed using the straight-line method over the lesser of the life of the asset or the remaining term of the lease.
Number of business segments | Segment			1
Revenue | Maximum
Significant Accounting Policies [Line Items]
Percent of revenues			1.00%
Aircraft
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (in years)			7 years
Equipment
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (in years)			5 years
Furniture and Fixtures
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (in years)			7 years
Leasehold Improvements
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (in years)			10 years
Estimated useful lives of fixed assets, maximum (in years)			Lesser of 10 years or the remaining lease term
Restricted Stock | Minimum
Significant Accounting Policies [Line Items]
Restricted stock units, amortization service period (years)			4 years
Restricted Stock | Maximum
Significant Accounting Policies [Line Items]
Restricted stock units, amortization service period (years)			5 years
Capital advisory engagements
Significant Accounting Policies [Line Items]
Interest income	$ 0.2	$ 0.1	$ 0.5	$ 0.6

Cash and Cash Equivalents (Deta

Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2015
Restricted Cash and Cash Equivalents Items [Line Items]
Cash	$ 37,548	$ 85,047
Cash equivalents	8,832	9,013
Restricted cash - letters of credit	4,500	4,300
Total cash and cash equivalents	50,875	98,313	$ 55,819	$ 69,962
Letter of Credit
Restricted Cash and Cash Equivalents Items [Line Items]
Restricted cash - letters of credit	$ 4,495	$ 4,253

Other Assets - Carrying Value o

Other Assets - Carrying Value of Investments in Merchant Banking Funds (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses	$ 3,590	$ 4,295
Investments in merchant banking funds	1,202	1,689
Rent deposits	1,771	1,517
Other tangible assets	1,235	540
Intangible assets	100	300
Total other assets	$ 7,898	$ 8,341

Other Assets Narrative (Details

Other Assets Narrative (Details)	Sep. 30, 2017USD ($)
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Unfunded commitment	$ 0

Fair Value of Financial Instr31

Fair Value of Financial Instruments - Narrative (Details) - USD ($) $ in Thousands	Apr. 01, 2015	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Revenue target	$ 80,000
Contingent obligation due selling unitholders of Cogent		$ 9,456		$ 9,456		$ 15,095
Increase (decrease) in fair value contingent consideration				(5,639)	$ 1,422
Cogent Partners, LP
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maximum contingent consideration	$ 18,900
Conditional consideration (shares)	334,048
Distribution period ending on the second anniversary of the closing (years)	2 years
Distribution period ending on the fourth anniversary of the closing (years)	2 years
Contingent obligation due selling unitholders of Cogent	$ 13,100	9,600		9,600
Increase (decrease) in fair value contingent consideration		$ 1,900	$ 30	$ (5,600)	$ 1,400

Fair Value of Financial Instr32

Fair Value of Financial Instruments - Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent obligation due selling unitholders of Cogent	$ 9,456	$ 15,095
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent obligation due selling unitholders of Cogent	9,456	15,095
Total liabilities measured at fair value on a recurring basis	9,456	15,095
Fair Value, Measurements, Recurring | Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent obligation due selling unitholders of Cogent	0	0
Total liabilities measured at fair value on a recurring basis	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent obligation due selling unitholders of Cogent	0	0
Total liabilities measured at fair value on a recurring basis	0	0
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent obligation due selling unitholders of Cogent	9,456	15,095
Total liabilities measured at fair value on a recurring basis	$ 9,456	$ 15,095

Fair Value of Financial Instr33

Fair Value of Financial Instruments - Unobservable Input Reconciliation (Details) - Fair Value, Inputs, Level 3 [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening Balance	$ 7,582	$ 15,104	$ 15,095	$ 13,647
Total realized and unrealized gains (losses) included in Net Income	(1,874)	35	5,639	(1,422)
Unrealized gains (losses) included in Other Comprehensive Income	0	0	0	0
Purchases	0	0	0	0
Issues	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Closing Balance	9,456	15,069	9,456	15,069
Unrealized gains (losses) for Level 3 liabilities outstanding	(1,874)	35	5,639	(1,422)
Contingent Consideration Liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening Balance	7,582	15,104	15,095	13,647
Total realized and unrealized gains (losses) included in Net Income	(1,874)	35	5,639	(1,422)
Unrealized gains (losses) included in Other Comprehensive Income	0	0	0	0
Purchases	0	0	0	0
Issues	0	0	0	0
Sales	0	0	0	0
Settlements	0	0	0	0
Closing Balance	9,456	15,069	9,456	15,069
Unrealized gains (losses) for Level 3 liabilities outstanding	$ (1,874)	$ 35	$ 5,639	$ (1,422)

Fair Value of Financial Instr34

Fair Value of Financial Instruments - Quantitative Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Dec. 31, 2016
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent obligation due selling unitholders of Cogent	$ 9,456	$ 15,095
Fair Value, Measurements, Recurring
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent obligation due selling unitholders of Cogent	9,456	15,095
Fair Value, Measurements, Recurring | Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent obligation due selling unitholders of Cogent	9,456	$ 15,095
Fair Value, Measurements, Recurring | Contingent Consideration Liability | Present value of expected payments | Significant Unobservable Inputs (Level 3)
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent obligation due selling unitholders of Cogent	$ 9,456
Fair Value, Measurements, Recurring | Contingent Consideration Liability | Present value of expected payments | Significant Unobservable Inputs (Level 3) | Weighted Average
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Discount Rate	13.00%

Related Parties - Additional In

Related Parties - Additional Information (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Nov. 09, 2017	Sep. 25, 2017	Dec. 31, 2016
Related Party Transaction [Line Items]
Common Stock, Value, Subscriptions						$ 20,000,000
Receivables (payables) to related parties	$ 0		$ 0				$ 0
Tenant reimbursements	$ 20,000	$ 20,000	$ 60,000	$ 50,000
Company's Chairman And Chief Executive Officer [Member]
Related Party Transaction [Line Items]
Common Stock, Value, Subscriptions						$ 10,000,000
Scenario, Forecast
Related Party Transaction [Line Items]
Common stock, shares issued (shares)					1,159,420

Bank Loan Facilities - Addition

Bank Loan Facilities - Additional Information (Details)	Apr. 30, 2018USD ($)	Oct. 12, 2017USD ($)	Apr. 30, 2015USD ($)Loaninstallment	Sep. 30, 2017USD ($)	Sep. 30, 2017USD ($)	Sep. 30, 2016USD ($)	Oct. 10, 2017USD ($)	Sep. 25, 2017USD ($)	Dec. 31, 2016USD ($)
Line of Credit Facility [Line Items]
Term loan facility				$ 0	$ 0				$ 16,875,000
Repayment of bank term loans					$ 16,875,000	$ 16,875,000
Cogent 12 Month Facility
Line of Credit Facility [Line Items]
Interest rate, percent			4.00%
Weighted average interest rate (percent)				5.17%	5.17%	4.67%
Cogent 36 Month Facility
Line of Credit Facility [Line Items]
Interest rate, percent			4.00%
Weighted average interest rate (percent)			1.25%
Term loan facility									$ 16,900,000
Debt instrument term (years)			3 years
Number of semi-annual installments (installment) | installment			4
Debt instrument, amount outstanding to reduce interest rate			$ 7,500,000
Repayment of bank term loans				$ 11,300,000
Cogent 36 Month Facility | Prime Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)			0.75%
Cogent Partners, LP
Line of Credit Facility [Line Items]
Term loan facility			$ 45,000,000
Number of bank term loan facilities (loan) | Loan			2
Cogent Partners, LP | Cogent 12 Month Facility | Short-term Debt
Line of Credit Facility [Line Items]
Term loan facility			$ 22,500,000
Cogent Partners, LP | Cogent 36 Month Facility | Long-term Debt
Line of Credit Facility [Line Items]
Term loan facility			$ 22,500,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving loan facility, maximum borrowing capacity				$ 90,000,000	$ 90,000,000
Increase in maximum borrowing capacity					$ 20,000,000
Interest rate, percent				3.50%	3.50%
Weighted average daily borrowings outstanding under the loan facility					$ 64,800,000	$ 52,200,000
Weighted average interest rate (percent)				4.04%	4.04%	3.50%
Revolving Credit Facility | Prime Rate
Line of Credit Facility [Line Items]
Basis spread on variable rate (percent)					4.25%
Revolving Credit Facility | Recapitalization Credit Agreement | Secured Debt | Subsequent Event
Line of Credit Facility [Line Items]
Revolving loan facility, maximum borrowing capacity		$ 20,000,000
Debt instrument term (years)		3 years
Term Loan | Recapitalization Credit Agreement | Secured Debt
Line of Credit Facility [Line Items]
Revolving loan facility, maximum borrowing capacity								$ 300,000,000
Term Loan | Recapitalization Credit Agreement | Secured Debt | Subsequent Event
Line of Credit Facility [Line Items]
Revolving loan facility, maximum borrowing capacity		$ 350,000,000
Debt instrument term (years)		5 years
Authorized Repurchase Program on September 25 [Member] | Common Stock
Line of Credit Facility [Line Items]
Stock repurchase program, authorized amount								$ 235,000,000
Authorized Repurchase Program on September 25 [Member] | Common Stock | Subsequent Event
Line of Credit Facility [Line Items]
Stock repurchase program, authorized amount							$ 285,000,000
Stock Repurchase Program On October 10 | Common Stock | Subsequent Event
Line of Credit Facility [Line Items]
Stock repurchase program, authorized amount							$ 285,000,000
Scenario, Forecast | Cogent 36 Month Facility
Line of Credit Facility [Line Items]
Repayment of bank term loans	$ 5,600,000

Equity - Additional Information

Equity - Additional Information (Details) - USD ($) $ / shares in Units, $ in Millions	Oct. 10, 2017	Sep. 27, 2017	Sep. 25, 2017	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Nov. 09, 2017
Stockholders Equity Note [Line Items]
Dividends declared and paid per share (usd per share)		$ 0.45		$ 0.45	$ 0.45	$ 1.35	$ 1.35
Dividend equivalents paid						$ 6.2	$ 6.4
Common stock, value, issued			$ 20
Common Stock
Stockholders Equity Note [Line Items]
Repurchased shares for award (shares)						448,738	319,194
Average repurchase price of shares for award (usd per share)						$ 29.06	$ 25.10
Treasury stock, shares, acquired (shares)							626,455
Treasury stock acquired, average cost per share							$ 20.22
Restricted Stock Units
Stockholders Equity Note [Line Items]
Restricted stock units vested and issued as common stock (shares)						1,095,224	850,387
Common Stock | Authorized Repurchase Program on September 25 [Member]
Stockholders Equity Note [Line Items]
Treasury stock acquired, average cost per share			$ 17
Stock repurchase program, authorized amount			$ 235
Stock repurchase program, number of shares authorized to be repurchased (in shares)			9,000,000
Company's Chairman And Chief Executive Officer [Member]
Stockholders Equity Note [Line Items]
Common stock, value, issued			$ 10
Scenario, Forecast
Stockholders Equity Note [Line Items]
Common stock, shares issued (shares)								1,159,420
Subsequent Event
Stockholders Equity Note [Line Items]
Common stock, value, issued								$ 20
Subsequent Event | Common Stock | Authorized Repurchase Program on September 25 [Member]
Stockholders Equity Note [Line Items]
Treasury stock acquired, average cost per share	$ 17.25
Stock repurchase program, authorized amount	$ 285
Stock repurchase program, number of shares authorized to be repurchased (in shares)	12,000,000
Subsequent Event | Company's Chairman And Chief Executive Officer [Member]
Stockholders Equity Note [Line Items]
Common stock, value, issued								$ 10
Subsequent Event | Scenario, Forecast
Stockholders Equity Note [Line Items]
Common stock, shares issued (shares)								1,159,420

Earnings per Share - Reconcilia

Earnings per Share - Reconciliation (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
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from EPS (shares)	256		35,877
Numerator for basic and diluted EPS — net income (loss) allocated to common stockholders	$ (5,912)	$ 13,110	$ (413)	$ 37,095
Denominator for basic EPS — weighted average number of shares (shares)	32,280,535	31,686,347	32,371,356	31,953,530
Add — dilutive effect of:
Weighted average number of incremental shares issuable from restricted stock units (shares)	0	7,000	0	7,000
Denominator for diluted EPS — weighted average number of shares and dilutive potential shares (shares)	32,280,535	31,693,173	32,371,356	31,960,892
Earnings per share:
Basic (usd per share)	$ (0.18)	$ 0.41	$ (0.01)	$ 1.16
Diluted (usd per share)	$ (0.18)	$ 0.41	$ (0.01)	$ 1.16
Cogent Partners, LP
Antidilutive Securities Excluded from Computation of Earnings Per Share [Line Items]
Antidilutive securities excluded from EPS (shares)			334,048

Income Taxes (Details)

Income Taxes (Details) $ in Millions	9 Months Ended
	Sep. 30, 2017USD ($)
Income Tax Disclosure [Abstract]
Excess tax benefit	$ 1.1

Regulatory Requirements - Addit

Regulatory Requirements - Additional Information (Details)	9 Months Ended
	Sep. 30, 2017USD ($)
Regulatory Capital Requirements [Abstract]
Minimum net capital required	$ 5,000
Net capital	5,200,000
Excess net capital	$ 4,600,000
Aggregate indebtedness to net capital ratio (percent)	1.6
Description of minimum net capital requirements	The greater of $5,000 or 1/15 of aggregate indebtedness
Minimum net capital requirements (percent)	6.67%

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) - USD ($)	Dec. 31, 2018	Oct. 25, 2017	Oct. 18, 2017	Oct. 12, 2017	Oct. 10, 2017	Apr. 30, 2015	Sep. 30, 2018	Sep. 30, 2022	Nov. 09, 2017	Sep. 30, 2017	Sep. 25, 2017
Subsequent Event [Line Items]
Common Stock, Value, Subscriptions											$ 20,000,000
Subsequent Event
Subsequent Event [Line Items]
Dividends declared per common share (usd per share)			$ 0.05
Common stock, shares issued (shares)		3,434,137
Sale of stock consideration received		$ 59.2
Common Stock, Value, Subscriptions									$ 20,000,000
Revolving Credit Facility
Subsequent Event [Line Items]
Revolving loan facility, maximum borrowing capacity										$ 90,000,000
Cogent 36 Month Facility
Subsequent Event [Line Items]
Debt instrument term (years)						3 years
Common Stock | Subsequent Event
Subsequent Event [Line Items]
Sale of stock, price per share (in USD per share)		$ 17.25
Common Stock | Stock Repurchase Program On October 10 | Subsequent Event
Subsequent Event [Line Items]
Stock repurchase program, authorized amount					$ 285,000,000
Stock repurchase program, number of shares authorized to be repurchased (in shares)					12,000,000
Treasury stock acquired, average cost per share					$ 17.25
Secured Debt | Recapitalization Credit Agreement | Term Loan
Subsequent Event [Line Items]
Revolving loan facility, maximum borrowing capacity											$ 300,000,000
Secured Debt | Recapitalization Credit Agreement | Term Loan | Subsequent Event
Subsequent Event [Line Items]
Revolving loan facility, maximum borrowing capacity				$ 350,000,000
Debt instrument term (years)				5 years
Amendment penalty, percentage of principal amount				101.00%
Secured Debt | Recapitalization Credit Agreement | Revolving Credit Facility | Subsequent Event
Subsequent Event [Line Items]
Revolving loan facility, maximum borrowing capacity				$ 20,000,000
Debt instrument term (years)				3 years
Covenant, leverage ratio, excess borrowings, minimum				$ 12,500,000
Secured Debt | Base Rate | Recapitalization Credit Agreement | Subsequent Event
Subsequent Event [Line Items]
Basis spread on variable rate (percent)				2.75%
Secured Debt | London Interbank Offered Rate (LIBOR) | Recapitalization Credit Agreement | Subsequent Event
Subsequent Event [Line Items]
Basis spread on variable rate (percent)				3.75%
Scenario, Forecast
Subsequent Event [Line Items]
Common stock, shares issued (shares)									1,159,420
Scenario, Forecast | Subsequent Event
Subsequent Event [Line Items]
Common stock, shares issued (shares)									1,159,420
Scenario, Forecast | Secured Debt | Recapitalization Credit Agreement | Term Loan
Subsequent Event [Line Items]
Quarterly payment of principal							$ 4,375,000	$ 8,750,000
Annual principal payment								$ 35,000,000
Annual principal payment, percentage of excess cash flow	50.00%
United States | Secured Debt | Recapitalization Credit Agreement | Subsequent Event
Subsequent Event [Line Items]
Collateral, capital stock of subsidiary, percent				100.00%
Non-US | Secured Debt | Recapitalization Credit Agreement | Subsequent Event
Subsequent Event [Line Items]
Collateral, capital stock of subsidiary, percent				65.00%