Greenhill & Co (GHL) 10-K 28 Feb 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Feb. 15, 2018	Jun. 30, 2017
Document Documentand Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2017
Document Fiscal Year Focus	2,017
Document Fiscal Period Focus	FY
Trading Symbol	GHL
Entity Registrant Name	GREENHILL & CO INC
Entity Central Index Key	1,282,977
Current Fiscal Year End Date	--12-31
Entity Well-known Seasoned Issuer	No
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		27,303,100
Entity Public Float			$ 526

Consolidated Statements of Fina

Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets
Cash and cash equivalents ($3.9 million and $4.3 million restricted from use at December 31, 2017 and 2016, respectively)	$ 267,646	$ 98,313
Advisory fees receivable, net of allowance for doubtful accounts of $0.3 million and $0.0 million at December 31, 2017 and 2016, respectively	64,244	68,140
Other receivables	3,964	2,830
Property and equipment, net of accumulated depreciation of $62.1 and $59.0 million at December 31, 2017 and 2016	8,602	8,764
Goodwill	217,737	208,186
Deferred tax asset, net	42,345	62,108
Other assets	6,279	8,341
Total assets	610,817	456,682
Liabilities and Equity
Compensation payable	26,022	37,527
Accounts payable and accrued expenses	15,443	9,297
Current income taxes payable	5,311	18,968
Bank revolving loan payable	0	64,070
Bank term loans payable	0	16,875
Secured term loan payable	339,048	0
Contingent obligation due selling unitholders of Cogent	13,763	15,095
Deferred tax liability	2,928	3,667
Total liabilities	402,515	165,499
Common stock, par value $0.01 per share; 100,000,000 shares authorized, 43,750,170 and 41,377,614 shares issued as of December 31, 2017 and 2016, respectively; 27,084,520 and 28,981,189 shares outstanding as of December 31, 2017 and 2016, respectively	438	414
Restricted stock units	80,512	85,907
Additional paid-in capital	800,806	734,728
Exchangeable shares of subsidiary; 257,156 shares issued as of December 31, 2017 and 2016; 32,804 shares outstanding as of December 31, 2017 and 2016	1,958	1,958
Retained earnings	37,595	111,798
Accumulated other comprehensive income (loss)	(22,222)	(32,398)
Treasury stock, at cost, par value $0.01 per share; 16,665,650 and 12,396,425 shares as of December 31, 2017 and 2016, respectively	(690,785)	(611,224)
Stockholders’ equity	208,302	291,183
Total liabilities and equity	$ 610,817	$ 456,682

Consolidated Statements of Fin3

Consolidated Statements of Financial Condition (Parenthetical) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Statement of Financial Position [Abstract]
Cash and cash equivalents, restricted from use	$ 3,900	$ 4,300
Advisory fees receivable, allowance for doubtful accounts	300	0
Property and equipment, accumulated depreciation	$ 62,074	$ 58,997
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)	43,750,170	41,377,614
Common stock, shares outstanding (shares)	27,084,520	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)	16,665,650	12,396,425

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenues
Advisory revenues	$ 237,997	$ 334,787	$ 260,281
Investment revenues	1,185	732	1,279
Total revenues	239,182	335,519	261,560
Operating Expenses
Employee compensation and benefits	160,201	182,478	147,200
Occupancy and equipment rental	20,713	19,553	21,271
Depreciation and amortization	3,114	3,243	3,433
Information services	9,529	8,920	8,975
Professional fees	8,212	6,851	7,856
Travel related expenses	13,142	11,912	12,580
Other operating expenses	17,371	11,454	14,472
Total operating expenses	232,282	244,411	215,787
Total operating income	6,900	91,108	45,773
Interest expense	7,198	3,227	2,478
Income (loss) before taxes	(298)	87,881	43,295
Provision for taxes	26,353	27,119	17,697
Net income allocated to common stockholders	$ (26,651)	$ 60,762	$ 25,598
Average shares outstanding:
Basic (shares)	32,074,894	32,042,594	31,197,288
Diluted (shares)	32,074,894	32,074,232	31,200,378
Earnings (loss) per share:
Basic (usd per share)	$ (0.83)	$ 1.90	$ 0.82
Diluted (usd per share)	(0.83)	1.89	0.82
Dividends declared and paid per share (usd per share)	$ 1.4	$ 1.80	$ 1.80

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Consolidated net income (loss)	$ (26,651)	$ 60,762	$ 25,598
Currency translation adjustment, net of tax	10,176	(3,993)	(10,436)
Comprehensive income (loss) allocated to common stockholders	$ (16,475)	$ 56,769	$ 15,162

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock	Contingent convertible preferred stock	Restricted stock unitsRestricted stock units	Additional paid-in capital	Exchangeable shares of subsidiary	Retained earnings	Accumulated other comprehensive income	Treasury stock	Parent
Beginning Balance at Dec. 31, 2014		$ 389	$ 14,446	$ 90,107	$ 596,463	$ 1,958	$ 141,290	$ (17,969)	$ (571,136)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued		16			94,554
Contingent convertible preferred stock canceled or converted			(14,446)		(14,446)
Restricted stock units recognized, net of forfeitures				47,071
Restricted stock units delivered				(52,209)
Tax benefit (expense)					(7,856)		1,912
Exchangeable shares of subsidiary delivered						0
Dividends							(58,940)
Net income (loss) allocated to common stockholders	$ 25,598						25,598
Currency translation adjustment, net of tax	(10,436)							(10,436)
Repurchased									(11,902)
Ending Balance at Dec. 31, 2015		405	0	84,969	697,607	1,958	109,860	(28,405)	(583,038)	$ 283,356
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued		9			44,789
Contingent convertible preferred stock canceled or converted			0		0
Restricted stock units recognized, net of forfeitures				45,880
Restricted stock units delivered				(44,942)
Tax benefit (expense)					(7,668)		2,785
Exchangeable shares of subsidiary delivered						0
Dividends							(61,609)
Net income (loss) allocated to common stockholders	60,762						60,762
Currency translation adjustment, net of tax	(3,993)							(3,993)
Repurchased									(28,186)
Ending Balance at Dec. 31, 2016		414	0	85,907	734,728	1,958	111,798	(32,398)	(611,224)	291,183
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued		24			65,231
Contingent convertible preferred stock canceled or converted			0		0
Restricted stock units recognized, net of forfeitures				40,597
Restricted stock units delivered				(45,992)
Tax benefit (expense)					847		0
Exchangeable shares of subsidiary delivered						0
Dividends							(47,552)
Net income (loss) allocated to common stockholders	(26,651)						(26,651)
Currency translation adjustment, net of tax	$ 10,176							10,176
Repurchased									(79,561)
Ending Balance at Dec. 31, 2017		$ 438	$ 0	$ 80,512	$ 800,806	$ 1,958	$ 37,595	$ (22,222)	$ (690,785)	$ 208,302

Consolidated Statements of Cha7

Consolidated Statements of Changes in Equity (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
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	$ 0.01
Contingent Convertible Preferred Stock
Contingent convertible preferred stock, par value (usd per share)	0.01	0.01	0.01
Treasury Stock
Treasury stock, par value (usd per share)	$ 0.01	$ 0.01	$ 0.01

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating activities:
Consolidated net income (loss)	$ (26,651)	$ 60,762	$ 25,598
Non-cash items included in consolidated net income:
Depreciation and amortization	3,114	3,243	3,433
Net investment (gains) losses	258	255	(234)
Restricted stock units recognized	40,597	45,880	47,071
Deferred taxes	14,594	(7,457)	(6,058)
(Gain) loss on fair value of contingent obligation	(1,332)	1,448	503
Changes in operating assets and liabilities:
Advisory fees receivable	3,896	(3,710)	17,341
Other receivables and assets	449	1,509	(1,779)
Deferred tax asset, net	0	7,668	7,882
Compensation payable	(11,505)	15,394	(4,271)
Accounts payable and accrued expenses	5,409	(706)	(5,747)
Current income taxes payable	(13,657)	(52)	9,012
Net cash provided by operating activities	15,172	124,234	92,751
Investing activities:
Distributions from investments, net	221	937	832
Purchases of property and equipment	(2,555)	(1,737)	(2,242)
Contingent obligation due selling unitholders of Cogent	0	0	13,144
Cogent acquisition	0	0	(45,265)
Net cash used in investing activities	(2,334)	(800)	(33,531)
Financing activities:
Proceeds from revolving bank loan	69,355	105,999	80,000
Repayment of revolving bank loan	(133,425)	(81,729)	(75,800)
Proceeds from bank term loans	0	0	45,000
Repayment of bank term loans	(16,875)	(16,875)	(11,250)
Proceeds from secured term loan, net	339,048	0	0
Proceeds from Issuance of Common Stock	20,000	0	0
Dividends paid	(47,552)	(61,609)	(58,940)
Purchase of treasury stock	(79,561)	(28,186)	(11,902)
Net tax benefit (cost) from the delivery of restricted stock units and payment of dividend equivalents	0	(4,883)	(5,944)
Net cash provided by (used in) financing activities	150,990	(87,283)	(38,836)
Effect of exchange rate changes on cash and cash equivalents	5,505	(7,800)	(1,362)
Net increase in cash and cash equivalents	169,333	28,351	19,022
Cash and cash equivalents, beginning of year	98,313	69,962	50,940
Cash and cash equivalents, end of year	267,646	98,313	69,962
Supplemental disclosure of cash flow information:
Cash paid for interest	6,567	2,944	2,427
Cash paid for taxes, net of refunds	$ 26,026	$ 28,979	$ 14,445

Organization

Organization	12 Months Ended
	Dec. 31, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Organization	Note 1 — 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, Spain, 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. See "Note 3 — Acquisition". 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	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Note 2 — Summary of Significant Accounting Policies Basis of Financial Information These 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 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 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. 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 $4.7 million , $6.5 million and $5.4 million for the years ended December 31, 2017 , 2016 , and 2015 , 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, commercial paper, Treasury bills and short-term government bonds and are carried at cost, plus accrued interest, which approximates the fair value due to the short term nature of these investments. 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 4 — 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 $1.1 million , $0.4 million and $0.3 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Included in the advisory fees receivable balances at December 31, 2017 and 2016 were $29.3 million and $26.1 million 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 is interest income related to primary capital advisory engagements of $0.7 million , $0.8 million and $0.9 million for the years ended December 31, 2017 , 2016 and 2015 , 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 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 fund may apply discounts to reflect the lack of liquidity and other transfer restrictions. Compensation Payable Included in compensation payable are discretionary compensation awards comprised of annual cash bonuses and long-term incentive compensation, consisting of deferred cash retention awards, which are non-interest bearing, and generally amortized over a three to five year service period after the date of grant. See "Note 14 — Deferred Compensation". 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. In certain circumstances the Company issues share-based compensation, which is contingent on achievement of certain performance targets. Compensation expense for performance based awards begins at the time it is deemed more probable than not the performance target will be achieved and is amortized into expense over the remaining service period. 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 eligible for such payment 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 11 — 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. 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. 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. Income 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 consolidated statement of changes in stockholders' equity. Foreign currency transaction gains and losses are included in the consolidated statements of operations. 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 8 - Fair Value of Financial Instruments". Fair Value of Other Financial Instruments The Company believes that the carrying values of all financial instruments, other than certain cash equivalents, presented in the 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. Cash equivalents are categorized as Level 1 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 for the year ended December 31, 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 16 — Income Taxes ". Accounting Developments 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. 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 utilizing either a full retrospective or modified retrospective approach. The Company will adopt this standard effective on January 1, 2018 utilizing the modified retrospective approach. The Company has evaluated the impact of the 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), certain revenue of the Company, which is currently recognized at the time the services are provided, will now be recognized either at a point in time or over the term of an engagement. The change in Company's revenue recognition policy under the new revenue recognition model will create deferred revenue beginning in 2018 that will be recognized at a point in time as certain performance obligations are met. The Company estimates that as of January 1, 2018, the change will increase the Company's assets and liabilities by approximately $2.6 million and $10.2 million , respectively, and decrease retained earnings by approximately $7.6 million . The Company will also change the current presentation of certain reimbursed costs prospectively from a net to a gross presentation.

Acquisition

Acquisition	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Acquisition	Note 3 — Acquisition On April 1, 2015, the Company acquired 100% ownership of Cogent Partners, LP and its affiliates ("Cogent") (now known as our secondary capital advisory business), a global financial advisor to pension funds, endowments and other institutional investors on the secondary market for alternative assets, (the "Acquisition"). As consideration for the Acquisition the Company exchanged a combination of (i) $44.0 million in cash and 779,454 shares of Greenhill common stock paid at closing and (ii) $18.9 million in cash and 334,048 shares of Greenhill common stock payable in the future if certain agreed revenue targets are achieved (the "Earnout"). The cash component of the consideration paid at closing was funded by two bank term loan facilities, each in an original principal sum of $22.5 million , and together in aggregate $45.0 million . See "Note 10 — Loan Facilities". 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 year period ending on March 31, 2019, the contingent consideration will be paid promptly after that date. If the revenue target is not achieved during either of the two year Earnout periods, a payment will not be made. The fair value of the contingent issuance of common shares was valued on the date of the acquisition at $11.9 million and has been recorded as a component of stockholders' equity in the consolidated statements of financial condition. 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 December 31, 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 $13.8 million . For the year ended December 31, 2017 , the Company recognized a decrease in other operating expenses of $1.3 million , and for the years ended December 31, 2016 and 2015 an increase in other operating expenses of $1.5 million and $0.5 million , respectively. See "Note 8 — Fair Value of Financial Instruments", "Note 11 — Equity" and "Note 12 — Earnings per Share". The Acquisition has been accounted for using the purchase method of accounting and the results of operations for the acquired secondary capital advisory business have been included in the consolidated statements of operations from the date of acquisition. The Company incurred $1.2 million of transaction costs related to the Acquisition, which have been included as a component of professional fees in the consolidated statement of operations for the year ended December 31, 2015. An allocation of the total purchase price of approximately $100.0 million has been made to the assets acquired and liabilities assumed based on their fair values as of April 1, 2015, the date of the acquisition, as follows (in thousands): Allocation of assets acquired and liabilities assumed: Assets: Current assets $ 13,970 Property and equipment 599 Other assets 651 Identifiable intangible assets 1,300 Goodwill 93,116 Total assets 109,636 Liabilities: Current liabilities 9,640 Total liabilities 9,640 Net assets $ 99,996 The excess of the purchase price over the fair value of the net assets acquired of $93.1 million has been recorded as goodwill. Goodwill includes the in-place workforce, which allows the Company to continue serving its existing client base, begin marketing to potential clients and avoid significant costs reproducing the workforce. The fair value of the intangible assets acquired, which consist of Cogent's backlog of client assignments that existed at the time of the closing, customer relationships, and trade name, is based, in part, on a valuation using an income approach, market approach or cost approach and has been included in other assets on the consolidated statements of financial condition. The fair value ascribed to the identifiable intangible assets will be amortized on a straight-line basis over the remaining useful life of each asset over periods ranging between one to three years . The Company recorded amortization expense of $0.3 million for the year ended December 31, 2017 , and $0.5 million for each of the years ended December 31, 2016 and 2015 in respect of these assets. In addition, under the terms of the purchase, the sellers were entitled to receive a post-closing distribution for the amount of net working capital, as defined, as of March 31, 2015, in excess of $5.0 million . The amount distributable to the sellers was $7.9 million and was paid in 2015. Further, the total purchase included at the date of acquisition an escrow amount of $8.9 million , of which $8.4 million was paid to the sellers and $0.5 million was returned to the Company in 2016. The Acquisition was treated as an asset purchase for tax purposes. Similar to the purchase accounting method used for book purposes, the excess of the purchase price paid over the fair value of the net assets acquired was recorded as goodwill for tax purposes. The amount of goodwill recorded for tax purposes was determined based on the consideration paid at closing and is being amortized for tax purposes ratably over a fifteen years year period. If the Earnout is achieved, the additional consideration paid will also be treated as goodwill for tax purposes and will be amortized ratably over the remainder of the fifteen years period. For book purposes, the tax benefit from the amortization of goodwill is being recorded as an indefinite-lived deferred tax liability as it is realized. Consistent with the Company's normal personnel recruiting policies, and in order to provide long term incentives for retention and continued strong performance, the Company also granted restricted stock units and other deferred compensation awards to a number of Cogent employees, subject to continued employment. The awards will generally vest on the third or fifth anniversary of the closing. The awards have not been recorded as a component of the purchase price and will be expensed over the service period during which they are earned. Set forth below are the Company's summary unaudited pro forma results of operations for the year ended December 31, 2015 . The unaudited pro forma results of operations include the historical results of the Company and give effect to the Acquisition as if it had occurred on January 1, 2015. These pro forma results include the actual results of Cogent from January 1, 2015 through March 31, 2015. For the period April 1, 2015 through December 31, 2015, the results of the acquired secondary capital advisory business were included in the consolidated results of the Company. See "Note 12 — Earnings per Share". The unaudited pro forma results of operations do not purport to represent what the Company's results of operations would actually have been had the Acquisition occurred on January 1, 2015, as the case may be, or to project the Company's results of operations for any future period. Actual future results may vary considerably based on a variety of factors beyond the Company's control. For the Year Ended December 31, 2015 (in millions, except per share amounts) (unaudited) (pro forma) Revenues $ 272.0 Income before taxes 45.2 Net income allocated to common stockholders 26.8 Diluted earnings per share $ 0.84 The pro forma results include (i) compensation and benefits expense based upon a ratio of compensation to total revenues of 54% , which was the actual compensation ratio used by the Company in the pro forma periods presented, (ii) the amortization of identifiable intangible assets of Cogent, (iii) the estimated interest expense related to the bank term loan borrowings used to fund the Acquisition, (iv) the elimination of non-recurring revenue and expense items of Cogent which were directly attributable to the Acquisition, and (v) the estimated income tax expense related to Cogent's historical earnings, which as a result of the Acquisition, is subject to income tax at the effective tax rate of the Company.

Cash and Cash Equivalents

Cash and Cash Equivalents	12 Months Ended
	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Cash and Cash Equivalents	Note 4 — Cash and Cash Equivalents The carrying values of the Company's cash and cash equivalents are as follows: As of December 31, 2017 2016 (in thousands) Cash $ 70,459 $ 85,047 Cash equivalents 193,315 9,013 Restricted cash - letters of credit 3,872 4,253 Total cash and cash equivalents $ 267,646 $ 98,313 The carrying value of the Company's cash equivalents approximates fair value. See "Note 8 — Fair Value of Financial Instruments". Letters of credit were secured by cash held on deposit. See " Note 15 — Commitments and Contingencies ". Included as a component of investment revenues is interest income related to cash and cash equivalents of $0.6 million , $0.1 million and $0.2 million for the years ended December 31, 2017 , 2016 and 2015 , respectively.

Property and Equipment

Property and Equipment	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Property and Equipment	Note 5 — Property and Equipment Property and equipment consist of the following: As of December 31, 2017 2016 (in thousands) Aircraft $ 19,260 $ 19,160 Equipment 20,930 19,788 Furniture and fixtures 7,639 7,201 Leasehold improvements 22,847 21,612 70,676 67,761 Less accumulated depreciation and amortization (62,074 ) (58,997 ) Total property and equipment, net $ 8,602 $ 8,764

Goodwill

Goodwill	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Goodwill	Note 6 — Goodwill Goodwill consists of the following: As of December 31, 2017 2016 (in thousands) Balance, January 1 $ 208,186 $ 209,024 Foreign currency translation adjustments 9,551 (838 ) Balance, December 31 $ 217,737 $ 208,186 The Company performs a goodwill impairment test annually or more frequently if circumstances indicate that impairment may have occurred. The Company has reviewed its goodwill for potential impairment and determined that the fair value of goodwill exceeded the carrying value. Accordingly, no goodwill impairment loss has been recognized for the years ended December 31, 2017 , 2016 or 2015 .

Other Assets

Other Assets	12 Months Ended
	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Other Assets	Note 7 — Other Assets At December 31, 2017 , the Company had an investment in a previously sponsored merchant banking funds, Greenhill Capital Partners II (“GCP II”), and an interest in Barrow Street III, a real estate investment fund. At December 31, 2016 , the Company had investments in certain previously sponsored merchant banking funds: Greenhill Capital Partners I and GCP II, and an interest in Barrow Street III. At December 31, 2017 and 2016 , the Company had no remaining unfunded commitments. Other assets consist of the following: As of December 31, 2017 2016 (in thousands) Prepaid expenses $ 2,583 $ 4,295 Investments in merchant banking funds 1,209 1,689 Rent deposits 1,798 1,517 Other tangible assets 639 540 Intangible assets 50 300 Total other assets $ 6,279 $ 8,341 Investment revenues The Company’s generates investment revenues from its investments in merchant banking funds and interest income as follows: For the Years Ended December 31, 2017 2016 2015 (in thousands) Net realized and unrealized gains (losses) on investments in merchant banking funds $ (247 ) $ (210 ) $ 236 Interest income 1,432 942 1,043 Total investment revenues (losses) $ 1,185 $ 732 $ 1,279

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	Note 8 — Fair Value of Financial Instruments Assets and liabilities are classified in their entirety based on their lowest level of input that is significant to the fair value measurement. There were no Level 1 liabilities or Level 2 assets or liabilities measured at fair value during the year ended December 31, 2017 . There were no Level 1 or Level 2 assets or liabilities measured in the fair value hierarchy during the year ended December 31, 2016 . There were also no Level 3 assets measured at fair value during the years ended December 31, 2017 and 2016 . The following table sets forth the measurement at fair value on a recurring basis of the investments in money market fund and U.S. government securities. The securities are categorized as a Level 1 asset, as their valuation is based on quoted prices for identical assets in active markets. See " Note 4 — Cash and Cash Equivalents ". Assets Measured at Fair Value on a Recurring Basis as of December 31, 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 December 31, 2017 (in thousands) Assets Cash and cash equivalents $ 183,369 $ — $ — $ 183,369 Total $ 183,369 $ — $ — $ 183,369 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 and is categorized as a Level 3 liability. See "Note 3 — Acquisition". Liabilities Measured at Fair Value on a Recurring Basis as of December 31, 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 December 31, 2017 (in thousands) Liabilities Contingent obligation due selling unitholders of Cogent $ — $ — $ 13,763 $ 13,763 Total $ — $ — $ 13,763 $ 13,763 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) 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 year ended December 31, 2017 are as follows: 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 December 31, 2017 Unrealized gains (losses) for Level 3 liabilities outstanding at December 31, 2017 (in thousands) Liabilities Contingent obligation due selling unitholders of Cogent $ 15,095 $ 1,332 $ — $ — $ — $ — $ — $ 13,763 $ 1,332 Total $ 15,095 $ 1,332 $ — $ — $ — $ — $ — $ 13,763 $ 1,332 Changes in Level 3 liabilities measured at fair value on a recurring basis for the year ended December 31, 2016 are as follows: 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 December 31, 2016 Unrealized gains (losses) for Level 3 liabilities outstanding at December 31, 2016 (in thousands) Liabilities Contingent obligation due selling unitholders of Cogent $ 13,647 $ (1,448 ) $ — $ — $ — $ — $ — $ 15,095 $ (1,448 ) Total $ 13,647 $ (1,448 ) $ — $ — $ — $ — $ — $ 15,095 $ (1,448 ) Realized and unrealized gains (losses) are reported as a component of other operating expenses in the consolidated statements of operations. The following tables 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 December 31, 2017 : Fair Value as of December 31, 2017 Valuation Technique(s) Unobservable Input(s) Range (Weighted Average) (in thousands) Liabilities Contingent obligation due selling unitholders of Cogent $ 13,763 Present value of expected payments Discount rate 13 % Forecast revenue (a) The following tables 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 December 31, 2016 : Fair Value as of December 31, 2016 Valuation Technique(s) Unobservable Input(s) Range (Weighted Average) (in thousands) Liabilities Contingent obligation due selling unitholders of Cogent $ 15,095 Present value of expected payments Discount rate 13 % Forecast revenue (a) _____________________________________________ (a) The Company's estimate of contingent consideration as of December 31, 2017 and December 31, 2016 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	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Parties	Note 9 — Related Parties At December 31, 2017 and 2016 , the Company had no amounts payable to related parties. In November 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 11 — Equities". The Company subleases airplane and office space to a firm owned by the Chairman of the Company. The Company recognized rent reimbursements of $0.08 million , $0.07 million and $0.07 million , respectively, for the years ended December 31, 2017 , 2016 and 2015 , which are included as a reduction of occupancy and equipment rental on the consolidated statements of operations. During 2017 , 2016 and 2015 , the Company paid $0.01 million , $0.01 million and $0.04 million , respectively, for the use of an aircraft owned by the Chairman of the Company.

Loan Facilities

Loan Facilities	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Loan Facilities	Note 10 — Loan Facilities On October 12, 2017, as part of a recapitalization plan, the Company entered into a new credit agreement with a syndicate of lenders, who lent in face amount $350.0 million under a five -year secured term loan facility ("Term Loan Facility) and provided a three -year secured revolving credit facility ("Revolving Loan Facility") for $20.0 million , which was undrawn at closing. In conjunction with the borrowings under the credit facilities the Company incurred expenses of $11.5 million , consisting of original issue discount of $1.75 million and deferred financing costs of $9.8 million , which have been recorded as a reduction in the carrying value of the secured term loan in the consolidated statements of financial position. The closing costs of the credit facilities are being amortized into interest expense over the lives of the obligations. For the year ended December 31, 2017 the Company incurred incremental interest expense of $0.6 million related to the amortization of these costs. See "Note 11 — Equity". As of December 31, 2017 2016 (in thousands) Secured term loan $ 339,048 $ — Bank revolving loan — 64,070 Bank term loan — 16,875 Unamortized discount 1,663 — Unamortized debt issuance costs 9,289 — Total debt facilities 350,000 80,945 Current maturities of debt (21,875 ) (75,320 ) Total long-term debt $ 328,125 $ 5,625 Borrowings under the new credit facilities bear interest at either the U.S. Prime Rate plus 2.75% or LIBOR plus 3.75% . Borrowings under the Term Loan Facility had a weighted average interest rate for the period outstanding in 2017 of approximately 5.1% (with borrowing rate ranging from 5.0% to 5.3% during the period that the Term Facility was outstanding). The Term Loan Facility 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 repayments of principal within ninety days of year end 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. At December 31, 2017 , $350.0 million was outstanding on the Term Loan Facility and no amounts were outstanding under the Revolving Loan Facility. All mandatory repayments 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 Term Loan Facility and Revolving Loan Facility are both 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. At December 31, 2017 , the Company was compliant with all loan covenants. In conjunction with the borrowing of the Term Loan Facility in October 2017, the Company used a portion of the proceeds to repay in full outstanding borrowings of $83.8 million under the previously existing revolving bank loan facility plus accrued interest. Interest on the previous revolving bank loan facility was based on the higher of 3.50% or the U.S. Prime Rate ( 4.25% at the time of repayment) and was payable monthly. The weighted average daily borrowings outstanding under the previous revolving bank loan facility for the portion of the year the obligation was outstanding were approximately $65.3 million and $54.1 million for the years ended December 31, 2017 and 2016 , respectively. The weighted average interest rate was 4.1% for the period outstanding in 2017 , and 3.5% and 3.3% for the years ended December 31, 2016 and 2015 , 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, each in an original principal amount of $22.5 million . One bank term loan facility, which bore interest at the U.S. Prime Rate plus 0.75% , was repaid in two equal installments, one in June 2015 and the other in April 2016. The second bank term loan facility, which 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 was $7.5 million or less, had a maturity date of April 30, 2018 and was payable in four equal semi-annual installments beginning on October 31, 2016 . In 2016, a principal payment of $5.625 million was made on the second term loan facility. In 2017 , prior to the drawdown of the new credit facility, the Company repaid the outstanding balance of the term loan of $16.9 million 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 bank term loan facilities. The weighted average interest rate of the bank term loan facilities for the portion of the year the obligation was outstanding was 5.2% and 4.7% for the year ended December 31, 2017 and 2016 , respectively.

Equity

Equity	12 Months Ended
	Dec. 31, 2017
Stockholders' Equity Note [Abstract]
Equity	Note 11 — Equity In September 2017, the Company announced plans for a leveraged recapitalization, which included the authorization to repurchase up to $285 million of the Company's common stock. In connection with the recapitalization, in October 2017 the Company borrowed $350 million of secured term loans and repaid $83.8 million outstanding under the existing bank loan facilities. See “Note 10 — Loan Facilities”. In October 2017, the Company repurchased 3,434,137 shares of its common stock under the share repurchase plan through a tender offer at $17.25 per share for a total cash cost of approximately $59.2 million . In addition, the Company incurred fees and expenses relating to the tender offer of $0.7 million . In addition, during November and December 2017, the Company repurchased an additional 343,411 common shares through other open market transactions. Since commencement of its share repurchase plan, the Company repurchased in aggregate 3,777,548 shares of its common stock at an average price of $17.41 for a total cost of $65.8 million . At December 31, 2017, the Company had remaining authorization under its share repurchase plan of $219.2 million . See "Note 19 — Subsequent Events". In November 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 9 — Related Parties". In connection with the acquisition of Cogent, the Company issued 779,454 shares of common stock on the acquisition date, April 1, 2015. In addition, the Company will issue 334,048 shares of common stock shortly after the second or fourth anniversary of the Acquisition, as the case may be, if the revenue target related to the Earnout is achieved. If the revenue target related to the Earnout is not achieved the common shares will not be issued. The fair value of the contingent issuance of common shares was valued on the date of the acquisition at $11.9 million and has been recorded as additional paid in capital in the consolidated statements of financial condition. A portion of the value will be transferred to common stock if the Earnout is achieved. See "Note 3 — Acquisition" and " Note 12 — Earnings per Share ". During 2017 , 1,197,260 restricted stock units vested and were issued as common stock of which the Company is deemed to have repurchased 491,677 shares at an average price of $28.04 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 2016 , 852,218 restricted stock units vested and were issued as common stock of which the Company is deemed to have repurchased 319,573 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 2016 the Company repurchased in open market transactions 891,017 shares of its common stock at an average price of $22.63 . On December 20, 2017, a dividend of $0.05 per share was paid to stockholders of record on December 6, 2017. For the year ended December 31, 2017 , dividends declared per common share were $1.40 . For each of the years ended December 31, 2016 and 2015 , dividends declared per common share were $1.80 and are paid on outstanding common shares. In addition, dividend equivalent amounts are paid on outstanding restricted stock units and amounted to $6.3 million , $8.5 million and $6.5 million for the years ended December 31, 2017 , 2016 and 2015 , respectively, and are included in dividends paid on the consolidated statements of cash flows. In the event a restricted stock unit holder’s employment is terminated, a portion of the dividend equivalent amount is required to be paid back (a "clawback") to the Company and is netted against the dividend equivalent amounts. See “ Note 14 — Deferred Compensation - Restricted Stock Units”.

Earnings per Share

Earnings per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Earnings per Share	Note 12 — Earnings per Share The computations of basic and diluted EPS are set forth below: For the Years Ended December 31, 2017 2016 2015 (in thousands, except per share amounts) Numerator for basic and diluted EPS — net income (loss) allocated to common stockholders $ (26,651 ) $ 60,762 $ 25,598 Denominator for basic EPS — weighted average number of shares 32,075 32,043 31,197 Add — dilutive effect of: Weighted average number of incremental shares issuable from restricted stock units — (1) 31 3 Denominator for diluted EPS — weighted average number of shares and dilutive potential shares 32,075 32,074 31,200 Earnings (loss) per share: Basic $ (0.83 ) $ 1.90 $ 0.82 Diluted $ (0.83 ) $ 1.89 $ 0.82 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, the shares of common stock will not be issued. See “Note 3 — Acquisition” and "Note 11 — Equity". ________________________ (1) Excludes 223,438 shares for the year ended December 31, 2017 , which were considered antidilutive and thus were not included in the above calculation.

Retirement Plan

Retirement Plan	12 Months Ended
	Dec. 31, 2017
Retirement Benefits [Abstract]
Retirement Plan	Note 13 — Retirement Plan In the U.S., the Company sponsor qualified defined contribution plans (the “Retirement Plans”) covering all eligible employees of G&Co and GC LP The Retirement Plans provide for both employee contributions in accordance with Section 401(k) of the Internal Revenue Code, and employer discretionary profit sharing contributions, subject to statutory limits. The Company incurred costs of $0.6 million , $0.6 million and $0.3 million for contributions to the Retirement Plans for the years ended December 31, 2017 , 2016 and 2015 , respectively. There was $0.2 million and $0.5 million related to contributions due to the Retirement Plans included in compensation payable at December 31, 2017 and 2016 , respectively. GCI also operates a defined contribution pension fund for its employees. The assets of the pension fund are held separately in an independently administered fund. For the years ended December 31, 2017 , 2016 and 2015 , GCI incurred costs for the funding of pension contributions of approximately $0.3 million , $0.4 million and $0.5 million , respectively. At December 31, 2017 and 2016 , there were no amounts related to contributions due to the defined contribution pension fund included in compensation payable. Greenhill Australia is required by Australian law to contribute compulsory superannuation on employees' gross earnings, generally at a rate of 9% , subject to an annual limit per employee. Superannuation is a defined contribution plan in which retirement benefits are determined by the contribution accumulated over the working life plus investment earnings within the fund less expenses. Greenhill Australia incurred costs for the funding of pension contributions of approximately $0.4 million for each of the years ended December 31, 2017 and 2016 , respectively, and $0.5 million for the year ended December 31, 2015 . At December 31, 2017 and 2016 , there were no amounts related to superannuation contributions due to the defined contribution plan included in compensation payable.

Deferred Compensation

Deferred Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Deferred Compensation	Note 14 — Deferred Compensation Restricted Stock Units The Company has adopted an equity incentive plan to motivate its employees and allow them to participate in the ownership of its stock. Under the Company’s plan, restricted stock units, which represent a right to a future payment equal to one share of common stock, may be awarded to employees, directors and certain other non-employees as selected by the Compensation Committee. Awards granted under the plan generally vest ratably over a period of up to four to five years beginning on the first anniversary of the grant date or in full on the fourth or fifth anniversary of the grant date. To the extent the restricted stock units are outstanding at the time a dividend is paid on the common stock, a dividend equivalent amount is paid to the holders of the restricted stock units. In the event that the holder’s employment is terminated under circumstances in which units awarded under the plan are forfeited any dividend equivalent payments related to such forfeiture, which are unvested for accounting purposes, are required to be repaid to the Company. The activity related to the restricted stock units is set forth below: Restricted Stock Units Outstanding 2017 2016 Units Grant Date Weighted Average Fair Value Units Grant Date Weighted Average Fair Value Outstanding, January 1, 4,844,956 $ 33.38 3,723,129 $ 45.88 Granted 2,227,659 (1) 20.87 2,407,173 (2) 21.61 Delivered (1,219,193 ) (1) 37.38 (871,226 ) (2) 52.27 Forfeited (456,694 ) 24.76 (414,120 ) 37.66 Outstanding, December 31, 5,396,728 $ 28.02 4,844,956 $ 33.38 _____________________________________________ (1) Excludes 1,811,132 stock units granted and 931,180 stock units delivered to employees in connection with the annual awards granted and vested subsequent to December 31, 2017 as part of the long-term incentive awards program. (2) Excludes 973,946 stock units granted and 1,023,132 stock units delivered to employees in connection with the annual awards granted and vested subsequent to December 31, 2016 as part of the long-term incentive awards program. For the years ended December 31, 2017 , 2016 and 2015 , the Company recognized compensation expense from the amortization of restricted stock units, net of forfeitures, of $40.2 million , $45.8 million and $46.5 million , respectively. The weighted-average grant date fair value for restricted stock units granted during the years ended December 31, 2017 , 2016 and 2015 was $20.87 , $21.61 and $36.45 , respectively. As of December 31, 2017 , unrecognized restricted stock units compensation expense was approximately $60.1 million , with such unrecognized compensation expense expected to be recognized over a weighted average period of approximately 1.8 years. The Company issues restricted stock units to employees under the equity incentive plan, primarily in connection with its annual bonus awards and compensation agreements for new hires. In certain jurisdictions, the Company may settle share-based payment awards in cash in lieu of shares of common stock to obtain tax deductibility. In these circumstances, the awards are settled in the cash equivalent value of the Company's shares of common stock based upon their value at settlement date. These cash settled share-based awards are remeasured at fair value at each reporting period. The Company awarded 115,473 performance-based restricted stock awards ("PRSU"), as part of long-term incentive compensation in 2016. The PRSU award targeted performance from 2016 to 2018 to multi-year revenue, pre-tax profit and total stockholder return (“TSR”) goals, each equally weighted. If the achievement of a performance metric is below the threshold goal, the payout factor for such performance metric will be 0% . The maximum payout under the award is 288,683 units and the cumulative dividends over the reward period. The performance relative to revenue and pre-tax profit is measured quarterly and the probability weighted likelihood of achievement is recorded based on the grant day price. The TSR component is measured quarterly and the probability weighted likelihood of achievement is recorded based on the fair value at the date of grant. Deferred Cash Compensation As part of its long-term incentive award program, the Company grants deferred cash retention awards to certain eligible employees. The deferred awards, which generally vest over a three to five year service period or in full on the third or fifth anniversary of the grant date, provide the employee with the right to receive future cash compensation payments, which are non-interest bearing. Deferred cash compensation of $14.9 million and $7.0 million as of December 31, 2017 and 2016 , respectively is included in compensation payable in the consolidated statements of financial condition. As of December 31, 2017 , total unrecognized deferred cash compensation (prior to the consideration of forfeitures) was approximately $14.9 million and is expected to be recognized over a weighted-average period of 0.8 years . For the years ended December 31, 2017 , 2016 and 2015 , the Company recognized compensation expense from the amortization of deferred compensation, net of forfeitures, of $13.1 million , $4.8 million and $2.6 million , respectively.

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Note 15 — Commitments and Contingencies The Company has entered into certain leases for office space under non-cancellable operating lease agreements that expire on various dates through 2027. As of December 31, 2017 , the approximate aggregate minimum future rental payments required were as follows (in thousands): 2018 $ 16,144 2019 16,071 2020 13,727 2021 6,151 2022 3,867 Thereafter 8,106 Total (1) $ 64,066 _____________________________________________ (1) Minimum future rental payments are recorded at their gross amounts and have not been reduced by sublease rentals of $0.7 million for 2018 and $0.5 million for 2019 for approximately 7,000 of aggregate square footage for former Cogent office space in New York and London. The subleases extend through the terms of the existing leases, which both terminate in 2019. The Company has also entered into various operating leases for office equipment. Rent expense for leased office space, net of sublease reimbursements, for the years ended December 31, 2017 , 2016 and 2015 was approximately $15.0 million , $14.3 million and $16.0 million , respectively. Diversified financial institutions issued five letters of credit on behalf of the Company to secure office space leases, which totaled $3.9 million and $4.3 million at December 31, 2017 and 2016 , respectively. These letters of credit were secured by cash held on deposit. At December 31, 2017 and 2016 , no amounts had been drawn under any of the letters of credit. See " Note 4 — Cash and Cash Equivalents ". In addition, the Company has a contingent cash obligation of $18.9 million due the selling unit holders of Cogent if the Earnout is achieved. See "Note 3 — Acquisition" and "Note 8 — Fair Value of Financial Instruments". The Company is from time to time involved in legal proceedings incidental to the ordinary course of its business. The Company does not believe any such proceedings will have a material adverse effect on its results of operations.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	Note 16 — Income Taxes The Company is subject to U.S. federal, foreign, state and local corporate income taxes. The components of the provision for income taxes reflected on the consolidated statements of operations are set forth below: For the Years Ended December 31, 2017 2016 2015 (in thousands) Current taxes: U.S. federal $ 8,792 $ 19,392 $ 15,995 State and local 1,181 1,939 3,624 Foreign 1,786 13,245 4,136 Total current tax expense 11,759 34,576 23,755 Deferred taxes: U.S. federal 14,626 (4,530 ) (2,252 ) State and local 795 (321 ) (759 ) Foreign (827 ) (2,606 ) (3,047 ) Total deferred tax (benefit) expense 14,594 (7,457 ) (6,058 ) Total tax expense $ 26,353 $ 27,119 $ 17,697 The Company accounts for income taxes in accordance with ASC 740, which requires an asset and liability approach for financial accounting and reporting for income taxes. Deferred taxes are provided for the net tax effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. These deferred taxes are measured using the enacted tax rates and laws that will be in effect when such differences are expected to reverse. Recent changes in tax laws and enacted accounting pronouncements significantly affected the Company’s income tax provision in the current year. Effective in 2017, the Company was subject to a new accounting pronouncement which required it to record a charge or benefit in its income tax provision for the tax effect of the difference between the grant price value of restricted stock units and the market value of such awards at the time of vesting. In addition, this new pronouncement required the Company to record an income tax benefit for the tax effect of dividend payments on restricted stock units. In prior periods, the tax effect of these differences was recorded as a charge or benefit to stockholders equity. For the year ended December 31, 2017 , the Company incurred a net charge of $1.5 million related to this new accounting requirement. On December 22, 2017, the Tax Cuts and Jobs Act (the “TCJA”) was enacted making significant changes to U.S. corporate income tax laws by, among other things, lowering the corporate income tax rate from 35% to 21% beginning in 2018, imposing a one-time repatriation tax in the current year for the deemed repatriation of earnings of foreign subsidiaries previously tax deferred before the effective date of the legislation, and implementing a territorial-type tax system with a minimum tax for certain foreign earnings starting in 2018. Although the reduction in the corporate income tax rate is not effective until after the year ended December 31, 2017 , the legislation required the Company to revalue its deferred tax assets and liabilities and charge to deferred tax expense the future impact of the lower corporate tax rate as of the effective date of the legislation. In accordance with ASC 740, this revaluation adjustment includes the tax effect related to the change in corporate tax rates for foreign currency translation adjustments that had previously been accounted for as a tax adjustment in other comprehensive income in the consolidated statements of changes in stockholders' equity. The effect of the revaluation of the Company’s deferred tax assets and liabilities resulted in a net charge of $15.4 million for the year ended December 31, 2017 . Despite having significant tax deferred foreign earnings at the effective date of the legislation, the one-time repatriation tax charge for previously deferred earnings of foreign subsidiaries did not result in a charge in the tax provision for the year ended December 31, 2017 , because the calculation of the deemed repatriation allows the offset of cumulative foreign earning by jurisdiction against cumulative foreign losses of other jurisdictions. The implementation of a territorial-type tax system does not affect the tax provision for the year ended December 31, 2017 and is not expected to have a material impact in future years. As such, in order to better align its structure and operations with these new tax laws, the Company no longer intends to indefinitely reinvest its non-U.S. subsidiary earnings outside of the United States. Significant components of the Company's net deferred tax assets and liabilities are set forth below: As of December 31, 2017 2016 (in thousands) Deferred tax assets: Compensation and benefits $ 23,080 $ 32,021 Depreciation and amortization 1,521 2,483 Cumulative translation adjustment 8,878 20,361 Operating loss carryforwards 10,133 4,944 Capital loss carryforwards 2,106 1,938 Unrealized loss on investments 61 — Other financial accruals 2,047 2,299 Valuation allowances (5,481 ) (1,938 ) Total deferred tax assets 42,345 62,108 Deferred tax liabilities: Unrealized gain on investments — 659 Other financial accruals 2,928 3,008 Total deferred tax liabilities 2,928 3,667 Net deferred tax asset $ 39,417 $ 58,441 Based on the Company's historical taxable income and its expectation for taxable income in the future, management expects that its largest 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 future taxable income. The Company’s deferred taxes for operating loss carryforwards relate to losses incurred in foreign jurisdictions. In 2017 , although operating loss carryforwards increased in most foreign jurisdictions, these jurisdictions had been profitable in prior years and the Company believes it is more likely than not they will be profitable in future years. However, management has carefully considered the need for a valuation allowance by evaluating each foreign jurisdiction separately and considering items such as historical and estimated future taxable income, cost bases, and other various factors. Based on all available information, the Company has determined that it is more likely than not that it will realize the full benefit of these operating loss carryforwards and other deferred tax assets in the majority of its foreign jurisdictions. However, due to accounting requirements and other factors the Company has established valuation allowances for operating loss carryforwards and other deferred tax assets of $3.4 million . At December 31, 2017 , the Company had foreign operating loss carryforwards, which in aggregate totaled $37.4 million , including the reserved amounts and the additional amounts related to the new accounting pronouncement. These operating loss carryforwards may be carried forward for eight years and longer notwithstanding $0.6 million which can be carried forward for 4 years to 6 years . In addition to the valuation allowances against certain foreign operating loss carryforwards, the Company has previously recorded a valuation allowance against a deferred tax asset related to a capital loss carryforward in the United Kingdom. This capital loss was realized from the sale of an investment in the United Kingdom and can be carried forward indefinitely but can only be utilized against capital gain in the same jurisdiction. Since the Company has nominal remaining investments in the United Kingdom and considers it more likely than not that the Company will not generate a capital gain in the United Kingdom, the Company had previously established a full valuation allowance against this related deferred tax asset. As of December 31, 2017 , the amount of the deferred tax asset and corresponding valuation allowance for the capital loss carryforward in the United Kingdom was $2.1 million . This amount is greater than the prior year due to movement in the foreign currency exchange rate. Notwithstanding the tax effect of the change in corporate tax rates enacted by the TCJA, which has been included in deferred tax expense, any gain or loss resulting from the translation of deferred taxes for foreign affiliates has been included in the foreign currency translation adjustment as a component of other comprehensive income, net of tax, in the consolidated statements of changes in stockholders' equity. Income taxes receivable of $2.0 million and $1.4 million as of December 31, 2017 and 2016 , respectively, were included in other receivables in the consolidated statements of financial condition. The Company is subject to the income tax laws of the United States, its states and municipalities, and those of the foreign jurisdictions in which the Company operates. These laws are complex, and the manner in which they apply to the taxpayer's facts is sometimes open to interpretation. Management must make judgments in assessing the likelihood that a tax position will be sustained upon examination by the taxing authorities based on the technical merits of the tax position. In the normal course of business, the Company may be under audit in one or more of its jurisdictions in an open tax year for that particular jurisdiction. As of December 31, 2017 , the Company does not expect any material changes in its tax provision related to any current or future audits. The Company recognizes tax positions in the financial statements only when it is more likely than not that the position will be sustained on examination by the relevant taxing authority based on the technical merits of the position. A position that meets this standard is measured at the largest amount of benefit that will more likely than not be realized on settlement. A liability is established for differences between positions taken in a tax return and amounts recognized in the financial statements. The Company performed an analysis of its tax positions as of December 31, 2017 , and determined that there was no requirement to accrue any material additional liabilities. Also, when present as part of the tax provision calculation, interest and penalties have been reported as interest expense and other operating expenses in the consolidated statements of operations. A reconciliation of the statutory U.S. federal income tax rate of 35.0% to the Company’s effective income tax rate is set forth below: For the Years Ended December 31, 2017 2016 2015 U.S. statutory tax rate 35.0 % 35.0 % 35.0 % Increase related to state and local taxes, net of U.S. income tax benefit (499.9 ) 1.3 4.7 Benefits and taxes related to foreign operations (2,796.3 ) (6.2 ) 0.7 Accounting pronouncement for equity compensation including foreign (486.2 ) — — Rate change to deferred items related to Tax Cuts and Jobs Act (5,193.7 ) — — Other 89.2 0.8 0.5 Effective income tax rate (8,851.9 )% 30.9 % 40.9 % For the year ended December 31, 2017 , the rate reconciliation to 35.0% is not meaningful principally as result of the application of various material adjustments related to the TCJA on nominal pre-tax loss for the period.

Regulatory

Regulatory	12 Months Ended
	Dec. 31, 2017
Regulatory Capital Requirements [Abstract]
Regulatory	Note 17 — Regulatory 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 December 31, 2017 and 2016 , G&Co’s net capital was $5.0 million and $7.3 million , respectively, which exceeded its requirement by $4.0 million and $5.9 million , respectively. G&Co’s aggregate indebtedness to net capital ratio was 3.03 to 1 and 2.80 to 1 at December 31, 2017 and 2016 , respectively. Certain distributions and other capital withdrawals of G&Co are subject to certain notifications and restrictive provisions of the Rule. GC LP is also subject to the Rule. GCI, GCE and the European affiliate of GC LP are subject to capital requirements of the FCA. Greenhill Australia is subject to capital requirements of the ASIC. We are also subject to certain capital regulatory requirements in other jurisdictions. As of December 31, 2017 and 2016 , GCI, GCE, GC LP, Greenhill Australia, and our other regulated operations were in compliance with local capital adequacy requirements.

Business Information

Business Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Business Information	Note 18 — 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 generally generates less than 1% of its revenues from investment revenues, consisting of interest income and gains and losses on its remaining principal investments in merchant banking funds. The Company principally earns its revenues from advisory fees upon the successful completion of the client’s transaction or restructuring, or fund closing. Advisory revenues represented substantially all of the Company’s total revenues for the years ended December 31, 2017 , 2016 and 2015 , respectively. In 2017 and 2016 , there were no advisory clients that accounted for more than 10% of total revenues. Since the financial markets are global in nature, the Company generally manages its business based on the operating results of the enterprise taken as whole, not by geographic region. For reporting purposes, the geographic regions are the North America, Europe, and the rest of the world, which are the locations where the Company retains substantially all of its employees. The following table presents information about the Company by geographic region, after elimination of all significant inter-company accounts and transactions: As of or for the Years Ended December 31, 2017 2016 2015 (in thousands) Total revenues North America $ 169,502 $ 206,673 $ 172,582 Europe 47,441 110,229 63,875 Rest of World 22,239 18,617 25,103 Total $ 239,182 $ 335,519 $ 261,560 Income (loss) before taxes North America $ 15,315 $ 48,927 $ 40,895 Europe (10,547 ) 52,650 9,577 Rest of World (5,066 ) (13,696 ) (7,177 ) Total $ (298 ) $ 87,881 $ 43,295 Total assets North America $ 426,799 $ 266,975 $ 261,077 Europe 48,195 64,467 38,409 Rest of World 135,823 125,240 123,658 Total $ 610,817 $ 456,682 $ 423,144 The Company's revenues are based on the country where the services were derived. For the years ended December 31, 2017 , 2016 and 2015 , the Company generated 70% , 59% , and 66% , respectively, of its total revenues from the United States and 15% , 27% and 20% respectively, of its total revenues from the United Kingdom. No other country had revenues which individually represented more than 10% of the Company's total revenues during the years ended December 31, 2017 , 2016 and 2015 , respectfully. Included in the Company's total assets it had long-lived assets, excluding deferred tax assets and intangible assets, located in the United States of $ 36.6 million and $ 34.8 million at December 31, 2017 and 2016 , respectively. No other country had long- lived assets, which individually represented more than 10% of the Company's total long-lived assets at December 31, 2017 and 2016 .

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	Note 19 — Subsequent Events The Company evaluates subsequent events through the date on which the financial statements are issued. On February 6, 2018 , the Board of Directors of the Company declared a quarterly dividend of $0.05 per share. The dividend will be payable on March 21, 2018 to the common stockholders of record on March 7, 2018 . On February 13, 2018, the Company launched a modified Dutch auction tender offer to repurchase up to $110.0 million in value of its common stock at a price not greater than $20.50 per share nor less than $18.50 per share. The Company will determine from the prices specified by the tendering stockholders the lowest single price specified that will allow it to purchase the shares at an aggregate purchase price of up to $110.0 million . The tender offer is scheduled to expire on March 14, 2018, subject to extension. As of February 12, 2018, the Company had remaining share repurchase authorization of $212.7 million , which will be reduced to $102.7 million if the tender offer is fully subscribed. Following completion of the tender offer and the 10 business day period provided by the tender offer rules, the remainder of the $285.0 million share repurchase program may be implemented through open market purchases or other means. The price and timing of share repurchases, as well as the total funds ultimately expended, will be subject to market conditions and other factors.

Supplemental Financial Informat

Supplemental Financial Information Quarterly Results (unaudited)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Supplemental Financial Information Quarterly Results (unaudited)	Supplemental Financial Information Quarterly Results (unaudited) The following represents the Company’s unaudited quarterly results for the years ended December 31, 2017 and 2016 . These quarterly results were prepared in accordance with U.S. generally accepted accounting principles and reflect all adjustments that are, in the opinion of management, necessary for a fair presentation of the results. For the Three Months Ended March 31, June 30, Sept. 30, Dec. 31, (in millions, except per share data) Total revenues $ 56.9 $ 67.3 $ 48.1 $ 66.9 Total operating expenses 54.0 56.9 57.5 63.9 Total operating income (loss) 2.9 10.4 (9.4 ) 3.0 Interest expense 0.8 0.8 0.9 4.7 Income (loss) before taxes 2.1 9.6 (10.3 ) (1.7 ) Provision (benefit) for taxes 2.9 3.3 (4.4 ) 24.5 Net income (loss) allocated to common stockholders $ (0.8 ) $ 6.3 $ (5.9 ) $ (26.2 ) Earnings (loss) per share: Basic $ (0.02 ) $ 0.20 $ (0.18 ) $ (0.85 ) Diluted $ (0.02 ) $ 0.20 $ (0.18 ) $ (0.85 ) Dividends declared per share $ 0.45 $ 0.45 $ 0.45 $ 0.05 For the Three Months Ended March 31, June 30, Sept. 30, Dec. 31, (in millions, except per share data) Total revenues $ 66.9 $ 90.5 $ 76.6 $ 101.6 Total operating expenses 59.7 59.8 56.5 68.4 Total operating income 7.2 30.7 20.1 33.2 Interest expense 0.7 0.8 0.9 0.8 Income before taxes 6.5 29.9 19.2 32.4 Provision for taxes 2.1 10.2 6.1 8.7 Net income allocated to common stockholders $ 4.4 $ 19.7 $ 13.1 $ 23.7 Earnings per share: Basic $ 0.14 $ 0.62 $ 0.41 $ 0.74 Diluted $ 0.14 $ 0.62 $ 0.41 $ 0.74 Dividends declared per share $ 0.45 $ 0.45 $ 0.45 $ 0.45

Summary of Significant Accoun29

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Financial Information	Basis of Financial Information These 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 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 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.
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 $4.7 million , $6.5 million and $5.4 million for the years ended December 31, 2017 , 2016 , and 2015 , 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, commercial paper, Treasury bills and short-term government bonds and are carried at cost, plus accrued interest, which approximates the fair value due to the short term nature of these investments. 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.
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 $1.1 million , $0.4 million and $0.3 million for the years ended December 31, 2017 , 2016 and 2015 , respectively. Included in the advisory fees receivable balances at December 31, 2017 and 2016 were $29.3 million and $26.1 million 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 is interest income related to primary capital advisory engagements of $0.7 million , $0.8 million and $0.9 million for the years ended December 31, 2017 , 2016 and 2015 , 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 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 fund may apply discounts to reflect the lack of liquidity and other transfer restrictions.
Compensation Payable	Compensation Payable Included in compensation payable are discretionary compensation awards comprised of annual cash bonuses and long-term incentive compensation, consisting of deferred cash retention awards, which are non-interest bearing, and generally amortized over a three to five year service period after the date of grant.
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. In certain circumstances the Company issues share-based compensation, which is contingent on achievement of certain performance targets. Compensation expense for performance based awards begins at the time it is deemed more probable than not the performance target will be achieved and is amortized into expense over the remaining service period. 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 eligible for such payment 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 11 — 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.
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. 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. Income 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 consolidated statement of changes in stockholders' equity. Foreign currency transaction gains and losses are included in the consolidated statements of operations.
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 8 - Fair Value of Financial Instruments". Fair Value of Other Financial Instruments The Company believes that the carrying values of all financial instruments, other than certain cash equivalents, presented in the 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. Cash equivalents are categorized as Level 1 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; 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 for the year ended December 31, 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 16 — Income Taxes ". Accounting Developments 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. 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 utilizing either a full retrospective or modified retrospective approach. The Company will adopt this standard effective on January 1, 2018 utilizing the modified retrospective approach. The Company has evaluated the impact of the 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), certain revenue of the Company, which is currently recognized at the time the services are provided, will now be recognized either at a point in time or over the term of an engagement. The change in Company's revenue recognition policy under the new revenue recognition model will create deferred revenue beginning in 2018 that will be recognized at a point in time as certain performance obligations are met. The Company estimates that as of January 1, 2018, the change will increase the Company's assets and liabilities by approximately $2.6 million and $10.2 million , respectively, and decrease retained earnings by approximately $7.6 million . The Company will also change the current presentation of certain reimbursed costs prospectively from a net to a gross presentation.

Acquisition (Tables)

Acquisition (Tables)	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Purchase Price Allocation	An allocation of the total purchase price of approximately $100.0 million has been made to the assets acquired and liabilities assumed based on their fair values as of April 1, 2015, the date of the acquisition, as follows (in thousands): Allocation of assets acquired and liabilities assumed: Assets: Current assets $ 13,970 Property and equipment 599 Other assets 651 Identifiable intangible assets 1,300 Goodwill 93,116 Total assets 109,636 Liabilities: Current liabilities 9,640 Total liabilities 9,640 Net assets $ 99,996
Pro Forma Information	The unaudited pro forma results of operations do not purport to represent what the Company's results of operations would actually have been had the Acquisition occurred on January 1, 2015, as the case may be, or to project the Company's results of operations for any future period. Actual future results may vary considerably based on a variety of factors beyond the Company's control. For the Year Ended December 31, 2015 (in millions, except per share amounts) (unaudited) (pro forma) Revenues $ 272.0 Income before taxes 45.2 Net income allocated to common stockholders 26.8 Diluted earnings per share $ 0.84

Cash and Cash Equivalents (Tabl

Cash and Cash Equivalents (Tables)	12 Months Ended
	Dec. 31, 2017
Cash and Cash Equivalents [Abstract]
Schedule of Carrying Values of Cash and Cash Equivalents	The carrying values of the Company's cash and cash equivalents are as follows: As of December 31, 2017 2016 (in thousands) Cash $ 70,459 $ 85,047 Cash equivalents 193,315 9,013 Restricted cash - letters of credit 3,872 4,253 Total cash and cash equivalents $ 267,646 $ 98,313

Property and Equipment (Tables)

Property and Equipment (Tables)	12 Months Ended
	Dec. 31, 2017
Property, Plant and Equipment [Abstract]
Components of Property and Equipment	Property and equipment consist of the following: As of December 31, 2017 2016 (in thousands) Aircraft $ 19,260 $ 19,160 Equipment 20,930 19,788 Furniture and fixtures 7,639 7,201 Leasehold improvements 22,847 21,612 70,676 67,761 Less accumulated depreciation and amortization (62,074 ) (58,997 ) Total property and equipment, net $ 8,602 $ 8,764

Goodwill (Tables)

Goodwill (Tables)	12 Months Ended
	Dec. 31, 2017
Goodwill and Intangible Assets Disclosure [Abstract]
Changes in Carrying Value of Goodwill	Goodwill consists of the following: As of December 31, 2017 2016 (in thousands) Balance, January 1 $ 208,186 $ 209,024 Foreign currency translation adjustments 9,551 (838 ) Balance, December 31 $ 217,737 $ 208,186

Other Assets (Tables)

Other Assets (Tables)	12 Months Ended
	Dec. 31, 2017
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Schedule of Other Assets	Other assets consist of the following: As of December 31, 2017 2016 (in thousands) Prepaid expenses $ 2,583 $ 4,295 Investments in merchant banking funds 1,209 1,689 Rent deposits 1,798 1,517 Other tangible assets 639 540 Intangible assets 50 300 Total other assets $ 6,279 $ 8,341
Schedule of Investment Revenues	The Company’s generates investment revenues from its investments in merchant banking funds and interest income as follows: For the Years Ended December 31, 2017 2016 2015 (in thousands) Net realized and unrealized gains (losses) on investments in merchant banking funds $ (247 ) $ (210 ) $ 236 Interest income 1,432 942 1,043 Total investment revenues (losses) $ 1,185 $ 732 $ 1,279

Fair Value of Financial Instr35

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Liabilities Measured at Fair Value on a Recurring Basis	The following table sets forth the measurement at fair value on a recurring basis of the investments in money market fund and U.S. government securities. The securities are categorized as a Level 1 asset, as their valuation is based on quoted prices for identical assets in active markets. See " Note 4 — Cash and Cash Equivalents ". Assets Measured at Fair Value on a Recurring Basis as of December 31, 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 December 31, 2017 (in thousands) Assets Cash and cash equivalents $ 183,369 $ — $ — $ 183,369 Total $ 183,369 $ — $ — $ 183,369 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 and is categorized as a Level 3 liability. See "Note 3 — Acquisition". Liabilities Measured at Fair Value on a Recurring Basis as of December 31, 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 December 31, 2017 (in thousands) Liabilities Contingent obligation due selling unitholders of Cogent $ — $ — $ 13,763 $ 13,763 Total $ — $ — $ 13,763 $ 13,763 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) Liabilities Contingent obligation due selling unitholders of Cogent $ — $ — $ 15,095 $ 15,095 Total $ — $ — $ 15,095 $ 15,095
Changes in Level 3 Measured at Fair Value	Changes in Level 3 liabilities measured at fair value on a recurring basis for the year ended December 31, 2017 are as follows: 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 December 31, 2017 Unrealized gains (losses) for Level 3 liabilities outstanding at December 31, 2017 (in thousands) Liabilities Contingent obligation due selling unitholders of Cogent $ 15,095 $ 1,332 $ — $ — $ — $ — $ — $ 13,763 $ 1,332 Total $ 15,095 $ 1,332 $ — $ — $ — $ — $ — $ 13,763 $ 1,332 Changes in Level 3 liabilities measured at fair value on a recurring basis for the year ended December 31, 2016 are as follows: 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 December 31, 2016 Unrealized gains (losses) for Level 3 liabilities outstanding at December 31, 2016 (in thousands) Liabilities Contingent obligation due selling unitholders of Cogent $ 13,647 $ (1,448 ) $ — $ — $ — $ — $ — $ 15,095 $ (1,448 ) Total $ 13,647 $ (1,448 ) $ — $ — $ — $ — $ — $ 15,095 $ (1,448 )
Quantitative Information	The following tables 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 December 31, 2017 : Fair Value as of December 31, 2017 Valuation Technique(s) Unobservable Input(s) Range (Weighted Average) (in thousands) Liabilities Contingent obligation due selling unitholders of Cogent $ 13,763 Present value of expected payments Discount rate 13 % Forecast revenue (a) The following tables 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 December 31, 2016 : Fair Value as of December 31, 2016 Valuation Technique(s) Unobservable Input(s) Range (Weighted Average) (in thousands) Liabilities Contingent obligation due selling unitholders of Cogent $ 15,095 Present value of expected payments Discount rate 13 % Forecast revenue (a) _____________________________________________ (a) The Company's estimate of contingent consideration as of December 31, 2017 and December 31, 2016 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.

Loan Facilities (Tables)

Loan Facilities (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Schedule of Long-term Debt	As of December 31, 2017 2016 (in thousands) Secured term loan $ 339,048 $ — Bank revolving loan — 64,070 Bank term loan — 16,875 Unamortized discount 1,663 — Unamortized debt issuance costs 9,289 — Total debt facilities 350,000 80,945 Current maturities of debt (21,875 ) (75,320 ) Total long-term debt $ 328,125 $ 5,625

Earnings per Share (Tables)

Earnings per Share (Tables)	12 Months Ended
	Dec. 31, 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 Years Ended December 31, 2017 2016 2015 (in thousands, except per share amounts) Numerator for basic and diluted EPS — net income (loss) allocated to common stockholders $ (26,651 ) $ 60,762 $ 25,598 Denominator for basic EPS — weighted average number of shares 32,075 32,043 31,197 Add — dilutive effect of: Weighted average number of incremental shares issuable from restricted stock units — (1) 31 3 Denominator for diluted EPS — weighted average number of shares and dilutive potential shares 32,075 32,074 31,200 Earnings (loss) per share: Basic $ (0.83 ) $ 1.90 $ 0.82 Diluted $ (0.83 ) $ 1.89 $ 0.82

Deferred Compensation (Tables)

Deferred Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Restricted Stock Units Activity	The activity related to the restricted stock units is set forth below: Restricted Stock Units Outstanding 2017 2016 Units Grant Date Weighted Average Fair Value Units Grant Date Weighted Average Fair Value Outstanding, January 1, 4,844,956 $ 33.38 3,723,129 $ 45.88 Granted 2,227,659 (1) 20.87 2,407,173 (2) 21.61 Delivered (1,219,193 ) (1) 37.38 (871,226 ) (2) 52.27 Forfeited (456,694 ) 24.76 (414,120 ) 37.66 Outstanding, December 31, 5,396,728 $ 28.02 4,844,956 $ 33.38 _____________________________________________ (1) Excludes 1,811,132 stock units granted and 931,180 stock units delivered to employees in connection with the annual awards granted and vested subsequent to December 31, 2017 as part of the long-term incentive awards program. (2) Excludes 973,946 stock units granted and 1,023,132 stock units delivered to employees in connection with the annual awards granted and vested subsequent to December 31, 2016 as part of the long-term incentive awards program.

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments and Contingencies Disclosure [Abstract]
Approximate Aggregate Minimum Future Rental Payments Required	As of December 31, 2017 , the approximate aggregate minimum future rental payments required were as follows (in thousands): 2018 $ 16,144 2019 16,071 2020 13,727 2021 6,151 2022 3,867 Thereafter 8,106 Total (1) $ 64,066 _____________________________________________ (1) Minimum future rental payments are recorded at their gross amounts and have not been reduced by sublease rentals of $0.7 million for 2018 and $0.5 million for 2019 for approximately 7,000 of aggregate square footage for former Cogent office space in New York and London. The subleases extend through the terms of the existing leases, which both terminate in 2019.

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Components of Provision for Income Taxes	The components of the provision for income taxes reflected on the consolidated statements of operations are set forth below: For the Years Ended December 31, 2017 2016 2015 (in thousands) Current taxes: U.S. federal $ 8,792 $ 19,392 $ 15,995 State and local 1,181 1,939 3,624 Foreign 1,786 13,245 4,136 Total current tax expense 11,759 34,576 23,755 Deferred taxes: U.S. federal 14,626 (4,530 ) (2,252 ) State and local 795 (321 ) (759 ) Foreign (827 ) (2,606 ) (3,047 ) Total deferred tax (benefit) expense 14,594 (7,457 ) (6,058 ) Total tax expense $ 26,353 $ 27,119 $ 17,697
Significant Components of Net Deferred Tax Assets and Liabilities	Significant components of the Company's net deferred tax assets and liabilities are set forth below: As of December 31, 2017 2016 (in thousands) Deferred tax assets: Compensation and benefits $ 23,080 $ 32,021 Depreciation and amortization 1,521 2,483 Cumulative translation adjustment 8,878 20,361 Operating loss carryforwards 10,133 4,944 Capital loss carryforwards 2,106 1,938 Unrealized loss on investments 61 — Other financial accruals 2,047 2,299 Valuation allowances (5,481 ) (1,938 ) Total deferred tax assets 42,345 62,108 Deferred tax liabilities: Unrealized gain on investments — 659 Other financial accruals 2,928 3,008 Total deferred tax liabilities 2,928 3,667 Net deferred tax asset $ 39,417 $ 58,441
Reconciliation of Statutory U.S. Federal Income Tax Rate to Company's Effective Income Tax Rate	A reconciliation of the statutory U.S. federal income tax rate of 35.0% to the Company’s effective income tax rate is set forth below: For the Years Ended December 31, 2017 2016 2015 U.S. statutory tax rate 35.0 % 35.0 % 35.0 % Increase related to state and local taxes, net of U.S. income tax benefit (499.9 ) 1.3 4.7 Benefits and taxes related to foreign operations (2,796.3 ) (6.2 ) 0.7 Accounting pronouncement for equity compensation including foreign (486.2 ) — — Rate change to deferred items related to Tax Cuts and Jobs Act (5,193.7 ) — — Other 89.2 0.8 0.5 Effective income tax rate (8,851.9 )% 30.9 % 40.9 %

Business Information (Tables)

Business Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Information by Geographic Region, After Elimination of All Significant Inter-company Accounts and Transactions	The following table presents information about the Company by geographic region, after elimination of all significant inter-company accounts and transactions: As of or for the Years Ended December 31, 2017 2016 2015 (in thousands) Total revenues North America $ 169,502 $ 206,673 $ 172,582 Europe 47,441 110,229 63,875 Rest of World 22,239 18,617 25,103 Total $ 239,182 $ 335,519 $ 261,560 Income (loss) before taxes North America $ 15,315 $ 48,927 $ 40,895 Europe (10,547 ) 52,650 9,577 Rest of World (5,066 ) (13,696 ) (7,177 ) Total $ (298 ) $ 87,881 $ 43,295 Total assets North America $ 426,799 $ 266,975 $ 261,077 Europe 48,195 64,467 38,409 Rest of World 135,823 125,240 123,658 Total $ 610,817 $ 456,682 $ 423,144

Supplemental Financial Inform42

Supplemental Financial Information Quarterly Results (unaudited) (Tables)	12 Months Ended
	Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]
Unaudited Quarterly Results	The following represents the Company’s unaudited quarterly results for the years ended December 31, 2017 and 2016 . These quarterly results were prepared in accordance with U.S. generally accepted accounting principles and reflect all adjustments that are, in the opinion of management, necessary for a fair presentation of the results. For the Three Months Ended March 31, June 30, Sept. 30, Dec. 31, (in millions, except per share data) Total revenues $ 56.9 $ 67.3 $ 48.1 $ 66.9 Total operating expenses 54.0 56.9 57.5 63.9 Total operating income (loss) 2.9 10.4 (9.4 ) 3.0 Interest expense 0.8 0.8 0.9 4.7 Income (loss) before taxes 2.1 9.6 (10.3 ) (1.7 ) Provision (benefit) for taxes 2.9 3.3 (4.4 ) 24.5 Net income (loss) allocated to common stockholders $ (0.8 ) $ 6.3 $ (5.9 ) $ (26.2 ) Earnings (loss) per share: Basic $ (0.02 ) $ 0.20 $ (0.18 ) $ (0.85 ) Diluted $ (0.02 ) $ 0.20 $ (0.18 ) $ (0.85 ) Dividends declared per share $ 0.45 $ 0.45 $ 0.45 $ 0.05 For the Three Months Ended March 31, June 30, Sept. 30, Dec. 31, (in millions, except per share data) Total revenues $ 66.9 $ 90.5 $ 76.6 $ 101.6 Total operating expenses 59.7 59.8 56.5 68.4 Total operating income 7.2 30.7 20.1 33.2 Interest expense 0.7 0.8 0.9 0.8 Income before taxes 6.5 29.9 19.2 32.4 Provision for taxes 2.1 10.2 6.1 8.7 Net income allocated to common stockholders $ 4.4 $ 19.7 $ 13.1 $ 23.7 Earnings per share: Basic $ 0.14 $ 0.62 $ 0.41 $ 0.74 Diluted $ 0.14 $ 0.62 $ 0.41 $ 0.74 Dividends declared per share $ 0.45 $ 0.45 $ 0.45 $ 0.45

Organization (Details)

Organization (Details)	Dec. 31, 2017state
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of states in which entity is licensed to operate (states)	50

Summary of Significant Accoun44

Summary of Significant Accounting Policies (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2017USD ($)Segment	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Jan. 01, 2018USD ($)
Significant Accounting Policies [Line Items]
Client reimbursements	$ 4,700	$ 6,500	$ 5,400
Bad debt expense	1,100	400	300
Long term receivables related to primary capital advisory engagements	$ 29,300	26,100
Installments period	3 years
Interest income related to capital advisory engagements	$ 700	800	900
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) | Segment	1
Total assets	$ 610,817	456,682	$ 423,144
Liabilities	$ 402,515	$ 165,499
Revenue
Significant Accounting Policies [Line Items]
Percentage of revenues earned from interest income and investment gains (losses) on investments (less than)	1.00%
Aircraft
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (or lesser for Leaseholds)	7 years
Equipment
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (or lesser for Leaseholds)	5 years
Furniture and fixtures
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (or lesser for Leaseholds)	7 years
Leasehold improvements
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (or lesser for Leaseholds)	10 years
Estimated useful lives of fixed assets, description	Lesser of 10 years or the remaining lease term
Minimum
Significant Accounting Policies [Line Items]
Amortization period of deferred cash retention awards	3 years
Minimum | Restricted Stock
Significant Accounting Policies [Line Items]
Amortization period of restricted stock units	4 years
Maximum
Significant Accounting Policies [Line Items]
Amortization period of deferred cash retention awards	5 years
Maximum | Restricted Stock
Significant Accounting Policies [Line Items]
Amortization period of restricted stock units	5 years
Accounting Standards Update 2014-09 | Forecast
Significant Accounting Policies [Line Items]
Total assets				$ 2,600
Liabilities				10,200
Decrease in equity				$ 7,600

Acquisition - Narrative (Detail

Acquisition - Narrative (Details) $ in Thousands	Apr. 01, 2015USD ($)Loanshares	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Apr. 30, 2015USD ($)Loan	Mar. 31, 2015USD ($)
Business Acquisition [Line Items]
Payments to acquire Cogent Partners, LP		$ 0	$ 0	$ 45,265
Bank term loans payable		0	16,875
Revenue target for the Earnout	$ 80,000
Contingent obligation due selling unitholders of Cogent		13,763	15,095
Increase (decrease) in fair value of contingent obligation		(1,332)	1,448	503
Goodwill		217,737	208,186	209,024
Cogent Partners, LP
Business Acquisition [Line Items]
Ownership percent acquired	100.00%
Payments to acquire Cogent Partners, LP	$ 44,000
Common stock paid at acquisition closing (shares) | shares	779,454
Contingent consideration, cash	$ 18,900
Possible contingent consideration (shares) | shares	334,048
Number of bank term loan facilities (loan) | Loan	2				2
Bank term loans payable	$ 45,000				$ 45,000
Distribution period ending on the second anniversary of the closing	2 years
Distribution period ending on the fourth anniversary of the closing	2 years
Fair value of contingent common shares	$ 11,900
Contingent obligation due selling unitholders of Cogent	13,100	13,800
Increase (decrease) in fair value of contingent obligation		(1,300)	1,500	500
Transaction costs				1,200
Purchase price	100,000
Goodwill	93,116
Amortization expense		$ 300	500	500
Amount to trigger post-closing distribution payment						$ 5,000
Post closing distribution			$ 8,400	7,900
Escrow deposit	8,900
Portion of escrow returned to company				$ 500
Goodwill useful life		15 years
Ratio of compensation to total revenue				54.00%
Cogent Partners, LP | Minimum
Business Acquisition [Line Items]
Intangible assets useful life		1 year
Cogent Partners, LP | Maximum
Business Acquisition [Line Items]
Intangible assets useful life		3 years
Cogent Partners, LP | Short-term debt | Cogent 12 Month Facility
Business Acquisition [Line Items]
Bank term loans payable	$ 22,500				$ 22,500

Acquisition - Purchase Price Al

Acquisition - Purchase Price Allocation (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Apr. 01, 2015
Business Acquisition [Line Items]
Goodwill	$ 217,737	$ 208,186	$ 209,024
Cogent Partners, LP
Business Acquisition [Line Items]
Current assets				$ 13,970
Property and equipment				599
Other assets				651
Identifiable intangible assets				1,300
Goodwill				93,116
Total assets				109,636
Current liabilities				9,640
Total liabilities				9,640
Net assets				$ 99,996

Acquisition - Pro Forma Results

Acquisition - Pro Forma Results (Details) - Cogent Partners, LP $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015USD ($)$ / shares
Business Acquisition, Pro Forma Information, Nonrecurring Adjustment [Line Items]
Revenues	$ 272
Income before taxes	45.2
Net income allocated to common stockholders	$ 26.8
Diluted earnings per share (usd per share) | $ / shares	$ 0.84

Cash and Cash Equivalents (Deta

Cash and Cash Equivalents (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Cash and Cash Equivalents [Abstract]
Interest income related to cash and cash equivalents	$ 600	$ 100	$ 200
Restricted Cash and Cash Equivalents Items [Line Items]
Cash	70,459	85,047
Cash equivalents	193,315	9,013
Cash and cash equivalents, restricted from use	3,900	4,300
Total cash and cash equivalents	267,646	98,313
Letter of Credit
Restricted Cash and Cash Equivalents Items [Line Items]
Cash and cash equivalents, restricted from use	$ 3,872	$ 4,253

Property and Equipment - Compon

Property and Equipment - Components of Property and Equipment (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property, Plant and Equipment [Abstract]
Aircraft	$ 19,260	$ 19,160
Equipment	20,930	19,788
Furniture and fixtures	7,639	7,201
Leasehold improvements	22,847	21,612
Property, plant and equipment, gross	70,676	67,761
Less accumulated depreciation and amortization	(62,074)	(58,997)
Total property and equipment, net	$ 8,602	$ 8,764

Goodwill - Changes in Carrying

Goodwill - Changes in Carrying Value (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Goodwill
Balance, January 1	$ 208,186	$ 209,024
Foreign currency translation adjustments	9,551	(838)
Balance, December 31	$ 217,737	$ 208,186

Goodwill - Additional Informati

Goodwill - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Impairment loss	$ 0	$ 0	$ 0

Other Assets - Narrative (Detai

Other Assets - Narrative (Details) - USD ($)	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Unfunded commitments	$ 0	$ 0

Other Assets - Components of Ot

Other Assets - Components of Other Assets (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Prepaid expenses	$ 2,583	$ 4,295
Investments in merchant banking funds	1,209	1,689
Rent deposits	1,798	1,517
Other tangible assets	639	540
Intangible assets	50	300
Total other assets	$ 6,279	$ 8,341

Other Assets - Investment Reven

Other Assets - Investment Revenues (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract]
Net realized and unrealized gains (losses) on investments in merchant banking funds	$ (247)	$ (210)	$ 236
Interest income	1,432	942	1,043
Total investment revenues (losses)	$ 1,185	$ 732	$ 1,279

Fair Value of Financial Instr55

Fair Value of Financial Instruments - Fair Value on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Liabilities
Contingent obligation due selling unitholders of Cogent	$ 13,763	$ 15,095
Fair Value, Measurements, Recurring
Assets
Cash and cash equivalents	183,369
Assets, Fair Value Disclosure, Recurring	183,369
Liabilities
Contingent obligation due selling unitholders of Cogent	13,763	15,095
Liabilities	13,763	15,095
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fair Value, Measurements, Recurring
Assets
Cash and cash equivalents	183,369
Assets, Fair Value Disclosure, Recurring	183,369
Liabilities
Contingent obligation due selling unitholders of Cogent	0	0
Liabilities	0	0
Significant Other Observable Inputs (Level 2) | Fair Value, Measurements, Recurring
Assets
Cash and cash equivalents	0
Assets, Fair Value Disclosure, Recurring	0
Liabilities
Contingent obligation due selling unitholders of Cogent	0	0
Liabilities	0	0
Significant Unobservable Inputs (Level 3) | Fair Value, Measurements, Recurring
Assets
Cash and cash equivalents	0
Assets, Fair Value Disclosure, Recurring	0
Liabilities
Contingent obligation due selling unitholders of Cogent	13,763	15,095
Liabilities	$ 13,763	$ 15,095

Fair Value of Financial Instr56

Fair Value of Financial Instruments - Changes in Level 3 Liabilities (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening Balance	$ 15,095	$ 13,647
Total realized and unrealized gains (losses) included in Net Income	1,332	(1,448)
Unrealized gains (losses) included in Other Comprehensive Income	0	0
Purchases	0	0
Issues	0	0
Sales	0	0
Settlements	0	0
Closing Balance	13,763	15,095
Unrealized gains (losses) for Level 3 liabilities outstanding at December 31, 2017	1,332	(1,448)
Contingent Consideration Liability
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Opening Balance	15,095	13,647
Total realized and unrealized gains (losses) included in Net Income	1,332	(1,448)
Unrealized gains (losses) included in Other Comprehensive Income	0	0
Purchases	0	0
Issues	0	0
Sales	0	0
Settlements	0	0
Closing Balance	13,763	15,095
Unrealized gains (losses) for Level 3 liabilities outstanding at December 31, 2017	$ 1,332	$ (1,448)

Fair Value of Financial Instr57

Fair Value of Financial Instruments - Quantitative Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent obligation due selling unitholders of Cogent	$ 13,763	$ 15,095
Fair Value, Measurements, Recurring
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Contingent obligation due selling unitholders of Cogent	13,763	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	13,763	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	$ 13,763	$ 15,095
Fair Value, Measurements, Recurring | Contingent Consideration Liability | Present value of expected payments | Significant Unobservable Inputs (Level 3) | Range (Weighted Average)
Fair Value Inputs, Liabilities, Quantitative Information [Line Items]
Discount rate	13.00%	13.00%

Related Parties (Details)

Related Parties (Details) - USD ($)	1 Months Ended	12 Months Ended
	Nov. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Related Party Transaction [Line Items]
Due to affiliates		$ 0	$ 0
Sublease
Related Party Transaction [Line Items]
Rent reimbursements related to sublease		80,000	70,000	$ 70,000
Payment for use of aircraft owned by executive		$ 10,000	$ 10,000	$ 40,000
Chairman and Chief Executive Officer
Related Party Transaction [Line Items]
Company stock sold, total	$ 20,000,000
Total common shares issued (in shares)	1,159,420
Chairman
Related Party Transaction [Line Items]
Company stock sold per transaction	$ 10,000,000
Chief Executive Officer
Related Party Transaction [Line Items]
Company stock sold per transaction	$ 10,000,000

Loan Facilities - Additional In

Loan Facilities - Additional Information (Detail)

Oct. 12, 2017USD ($)

Oct. 31, 2017USD ($)

Apr. 30, 2016installment

Jun. 30, 2015installment

Apr. 30, 2015USD ($)Loaninstallment

Dec. 31, 2017USD ($)

Sep. 30, 2018USD ($)

Dec. 31, 2018

Dec. 31, 2017USD ($)

Dec. 31, 2016USD ($)

Dec. 31, 2015USD ($)

Sep. 30, 2022USD ($)

Apr. 01, 2015USD ($)Loan

Line of Credit Facility [Line Items]

Debt, discount

$ 1,663,000

$ 1,663,000

$ 0

Deferred financing costs

9,289,000

9,289,000

0

Bank term loans payable

$ 0

0

16,875,000

Repayments of bank term loans

$ 16,875,000

$ 16,875,000

$ 11,250,000

Cogent Partners, LP

Line of Credit Facility [Line Items]

Bank term loans payable

$ 45,000,000

$ 45,000,000

Number of bank term loan facilities (loan) | Loan

2

2

Revolving credit facility

Line of Credit Facility [Line Items]

Weighted average interest rate

4.10%

4.10%

3.50%

3.30%

Amount repaid

$ 83,800,000

Interest rate

3.50%

3.50%

Weighted average daily borrowings outstanding under the loan facility

$ 65,300,000

$ 54,100,000

Revolving credit facility | U.S. Prime Rate

Line of Credit Facility [Line Items]

Spread on interest rate

4.25%

Recapitalization credit agreement | Secured debt

Line of Credit Facility [Line Items]

Incurred expenses related to issuance of debt

$ 11,500,000

Debt, discount

1,750,000

Deferred financing costs

$ 9,800,000

Incremental expense related to the amortization of debt issuance costs

$ 600,000

Recapitalization credit agreement | Secured debt | United States

Line of Credit Facility [Line Items]

Collateral percentage, capital stock of subsidiary

100.00%

Recapitalization credit agreement | Secured debt | Non-US

Line of Credit Facility [Line Items]

Collateral percentage, capital stock of subsidiary

65.00%

Recapitalization credit agreement | Secured debt | Base rate

Line of Credit Facility [Line Items]

Spread on interest rate

2.75%

Recapitalization credit agreement | Secured debt | LIBOR

Line of Credit Facility [Line Items]

Spread on interest rate

3.75%

Recapitalization credit agreement | Secured debt | Term loan

Line of Credit Facility [Line Items]

Face amount of debt

$ 350,000,000

Percentage of redemption price

101.00%

Recapitalization credit agreement | Secured debt | Term loan | Forecast

Line of Credit Facility [Line Items]

Principal payments

$ 4,375,000

$ 8,750,000

Annual principal payments

$ 35,000,000

Period of time required before year end to make annual prepayments of principal

90 days

Annual prepayment of principal, percentage amount of annual excess cash flow

50.00%

Recapitalization credit agreement | Secured debt | Revolving credit facility

Line of Credit Facility [Line Items]

Covenant, leverage ratio, excess borrowings, minimum

$ 12,500,000

Term Loan Facility | Secured debt | Term loan

Line of Credit Facility [Line Items]

Face amount of debt

$ 350,000,000

Debt term

5 years

Long-term Debt, Weighted Average Interest Rate, over Time

5.10%

Amounts outstanding on lines of credit

350,000,000

$ 350,000,000

Term Loan Facility | Secured debt | Term loan | Minimum

Line of Credit Facility [Line Items]

Weighted average interest rate

5.00%

Term Loan Facility | Secured debt | Term loan | Maximum

Line of Credit Facility [Line Items]

Weighted average interest rate

5.30%

Revolving Loan Facility | Secured debt | Revolving credit facility

Line of Credit Facility [Line Items]

Face amount of debt

$ 20,000,000

Debt term

3 years

Amounts outstanding on lines of credit

$ 0

$ 0

Cogent 12 Month Facility

Line of Credit Facility [Line Items]

Weighted average interest rate

0.75%

5.20%

5.20%

4.70%

Number of equal payment installments | installment

1

1

2

Cogent 12 Month Facility | Cogent Partners, LP | Short-term debt

Line of Credit Facility [Line Items]

Bank term loans payable

$ 22,500,000

$ 22,500,000

Cogent 36 Month Facility

Line of Credit Facility [Line Items]

Weighted average interest rate

1.25%

Amount outstanding to reduce interest rate

$ 7,500,000

Repayments of bank term loans

$ 16,900,000

$ 5,625,000

Cogent 36 Month Facility | U.S. Prime Rate

Line of Credit Facility [Line Items]

Spread on interest rate

0.75%

Loan Facilities - Schedule of D

Loan Facilities - Schedule of Debt (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Debt Disclosure [Abstract]
Secured term loan payable	$ 339,048	$ 0
Bank revolving loan payable	0	64,070
Bank term loans payable	0	16,875
Unamortized discount	1,663	0
Unamortized debt issuance costs	9,289	0
Total debt facilities	350,000	80,945
Current maturities of debt	(21,875)	(75,320)
Total long-term debt	$ 328,125	$ 5,625

Equity (Details)

Equity (Details) - USD ($) $ / shares in Units, $ in Thousands	Dec. 20, 2017	Apr. 01, 2015	Nov. 30, 2017	Oct. 31, 2017	Dec. 31, 2017	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Equity, Class of Treasury Stock [Line Items]
Cost of repurchased common stock														$ 79,561	$ 28,186	$ 11,902
Dividends paid to stockholders (in dollars per share)	$ 0.05													$ 1.4	$ 1.80	$ 1.80
Dividends declared per common share (usd per share)						$ 0.05	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 1.40	$ 1.8	$ 1.80
Dividend equivalents paid on outstanding restricted stock units														$ 6,300	$ 8,500	$ 6,500
Common stock
Equity, Class of Treasury Stock [Line Items]
Repurchased common stock (shares)															891,017
Average repurchase price of common stock (usd per share)															$ 22.63
Restricted stock units
Equity, Class of Treasury Stock [Line Items]
Restricted stock units vested and issued as common stock (shares)									1,023,132					1,197,260	852,218
Repurchased shares for award (shares)														491,677	319,573
Average repurchase price of shares for award (usd per share)														$ 28.04	$ 25.10
Cogent Partners, LP
Equity, Class of Treasury Stock [Line Items]
Common stock issued on acquisition date (in shares)		779,454
Possible contingent consideration (shares)		334,048
Fair value of contingent common shares		$ 11,900
Chairman and Chief Executive Officer
Equity, Class of Treasury Stock [Line Items]
Company stock sold, total			$ 20,000
Total common shares issued (in shares)			1,159,420
Chairman
Equity, Class of Treasury Stock [Line Items]
Company stock sold per transaction			$ 10,000
Chief Executive Officer
Equity, Class of Treasury Stock [Line Items]
Company stock sold per transaction			$ 10,000
Term loan | Secured debt | Recapitalization credit agreement
Equity, Class of Treasury Stock [Line Items]
Amount borrowed				$ 350,000
Common stock
Equity, Class of Treasury Stock [Line Items]
Repurchased common stock (shares)					343,411
Share repurchase program, September 2017 | Common stock
Equity, Class of Treasury Stock [Line Items]
Authorized repurchase amount (up to)							$ 285,000
Repurchased common stock (shares)				3,434,137		3,777,548
Average repurchase price of common stock (usd per share)				$ 17.25										$ 17.41
Cost of repurchased common stock				$ 59,200		$ 65,800
Fees and expenses related to tender offer				$ 700
Remaining authorization under share repurchase plan					$ 219,200	$ 219,200								$ 219,200

Earnings per Share - Reconcilia

Earnings per Share - Reconciliation (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Numerator for basic and diluted EPS — net income (loss) allocated to common stockholders	$ (26,200)	$ (5,900)	$ 6,300	$ (800)	$ 23,700	$ 13,100	$ 19,700	$ 4,400	$ (26,651)	$ 60,762	$ 25,598
Denominator for basic EPS — weighted average number of shares (shares)									32,074,894	32,042,594	31,197,288
Add — dilutive effect of:
Weighted average number of incremental shares issuable from restricted stock units (shares)									0	31,000	3,000
Denominator for diluted EPS — weighted average number of shares and dilutive potential shares (shares)									32,074,894	32,074,232	31,200,378
Earnings (loss) per share:
Basic (usd per share)	$ (0.85)	$ (0.18)	$ 0.20	$ (0.02)	$ 0.74	$ 0.41	$ 0.62	$ 0.14	$ (0.83)	$ 1.90	$ 0.82
Diluted (usd per share)	$ (0.85)	$ (0.18)	$ 0.20	$ (0.02)	$ 0.74	$ 0.41	$ 0.62	$ 0.14	$ (0.83)	$ 1.89	$ 0.82

- Additional Information (Detai

- Additional Information (Details)	12 Months Ended
	Dec. 31, 2017shares
Earnings Per Share Disclosure [Line Items]
Antidilutive securities (shares)	223,438
Cogent Partners, LP
Earnings Per Share Disclosure [Line Items]
Antidilutive securities (shares)	334,048

Retirement Plan (Details)

Retirement Plan (Details) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Greenhill & Co., LLC
Defined Contribution Plan Disclosure [Line Items]
Incurred costs for contributions to retirement plan	$ 600,000	$ 600,000	$ 300,000
Contributions due to Retirement Plan included in compensation payable	200,000	500,000
Greenhill And Company International LLC
Defined Contribution Plan Disclosure [Line Items]
Contributions due to Retirement Plan included in compensation payable	0	0
Costs incurred for pension	300,000	400,000	500,000
Greenhill & Co. Australia Pty Limited
Defined Contribution Plan Disclosure [Line Items]
Contributions due to Retirement Plan included in compensation payable	0	0
Costs incurred for pension	$ 400,000	$ 400,000	$ 500,000
Greenhill & Co. Australia Pty Limited | Pension Plan
Defined Contribution Plan Disclosure [Line Items]
Contribution percent on employees' gross earnings (percent)	9.00%

Deferred Compensation - Additio

Deferred Compensation - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	2 Months Ended	3 Months Ended	12 Months Ended
	Feb. 28, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Share Based Payments Disclosure [Line Items]
Description of vesting term for awards granted			Awards granted under the plan generally vest ratably over a period of up to four to five years beginning on the first anniversary of the grant date or in full on the fourth or fifth anniversary of the grant date.
Unrecognized restricted stock units compensation expense			$ 14.9
Unrecognized restricted stock units compensation expense, weighted average recognition period			280 days
Deferred compensation payable			$ 14.9	$ 7
Compensation expense from deferred compensation			$ 13.1	4.8	$ 2.6
Minimum
Share Based Payments Disclosure [Line Items]
Service period for deferred compensation payable			3 years
Maximum
Share Based Payments Disclosure [Line Items]
Service period for deferred compensation payable			5 years
Restricted stock units
Share Based Payments Disclosure [Line Items]
Compensation expense from the vesting of restricted stock units			$ 40.2	$ 45.8	$ 46.5
Weighted average grant date fair value for restricted stock units granted (usd per share)			$ 20.87	$ 21.61	$ 36.45
Unrecognized restricted stock units compensation expense			$ 60.1
Unrecognized restricted stock units compensation expense, weighted average recognition period			1 year 9 months
Number of awards granted in the period (shares)		973,946	2,227,659	2,407,173
Restricted stock units vested and issued as common stock (shares)		1,023,132	1,197,260	852,218
Restricted stock units | Minimum
Share Based Payments Disclosure [Line Items]
Stock units granted, ratable vesting period			4 years
Restricted stock units | Maximum
Share Based Payments Disclosure [Line Items]
Stock units granted, ratable vesting period			5 years
Performance-Based Restricted Stock Units
Share Based Payments Disclosure [Line Items]
Number of awards granted in the period (shares)			115,473
Performance payout percentage, if performance thresholds not achieved			0.00%
Maximum number of awards issuable, if performance factors achieved (shares)			288,683
Subsequent event | Restricted stock units
Share Based Payments Disclosure [Line Items]
Number of awards granted in the period (shares)	1,811,132
Restricted stock units vested and issued as common stock (shares)	931,180

Deferred Compensation - Activit

Deferred Compensation - Activity (Detail) - Restricted stock units - $ / shares	2 Months Ended	3 Months Ended	12 Months Ended
	Feb. 28, 2018	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Units
Outstanding, beginning of period (shares)	5,396,728	4,844,956	4,844,956	3,723,129
Granted (shares)		973,946	2,227,659	2,407,173
Delivered (shares)			(1,219,193)	(871,226)
Forfeited (shares)			(456,694)	(414,120)
Outstanding, end of period (shares)			5,396,728	4,844,956	3,723,129
Grant Date Weighted Average Fair Value
Outstanding, beginning of period (usd per share)	$ 28.02	$ 33.38	$ 33.38	$ 45.88
Granted (usd per share)			20.87	21.61	$ 36.45
Delivered (usd per share)			37.38	52.27
Forfeited (usd per share)			24.76	37.66
Outstanding, end of period (usd per share)			$ 28.02	$ 33.38	$ 45.88
Subsequent event
Units
Granted (shares)	1,811,132

Commitments and Contingencies -

Commitments and Contingencies - Approximate Aggregate Minimum Future Rental Payments Required (Details) ft² in Thousands, $ in Thousands	Dec. 31, 2017USD ($)ft²
Operating Leased Assets
2,018	$ 16,144
2,019	16,071
2,020	13,727
2,021	6,151
2,022	3,867
Thereafter	8,106
Total	64,066
Sublease rentals due in one year	700
Sublease rentals due in two years	$ 500
Size of office space leased (sqft) | ft²	7,000

Commitments and Contingencies68

Commitments and Contingencies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)CreditFacility	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Apr. 01, 2015USD ($)
Commitments and Contingencies Disclosure [Line Items]
Rent expense	$ 15	$ 14.3	$ 16
Cogent Partners, LP
Commitments and Contingencies Disclosure [Line Items]
Contingent cash obligation				$ 18.9
Letter of Credit
Commitments and Contingencies Disclosure [Line Items]
Number of letters of credit issued to secure office space leases (credit facility) | CreditFacility	5
Amount outstanding on letters of credit	$ 3.9	$ 4.3

Income Taxes - Provision for In

Income Taxes - Provision for Income Taxes (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current taxes:
U.S. federal									$ 8,792	$ 19,392	$ 15,995
State and local									1,181	1,939	3,624
Foreign									1,786	13,245	4,136
Total current tax expense									11,759	34,576	23,755
Deferred taxes:
U.S. federal									14,626	(4,530)	(2,252)
State and local									795	(321)	(759)
Foreign									(827)	(2,606)	(3,047)
Total deferred tax (benefit) expense									14,594	(7,457)	(6,058)
Total tax expense	$ 24,500	$ (4,400)	$ 3,300	$ 2,900	$ 8,700	$ 6,100	$ 10,200	$ 2,100	$ 26,353	$ 27,119	$ 17,697

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclsoure [Line Items]
Net charge related to new accounting requirements for share-based compensation	$ 1,500
Revaluation of deferred tax assets and liabilities, resulting in a net charge	15,400
Valuation allowance for operating loss carryforwards and other deferred tax assets	3,400
Foreign loss carryforwards	37,400
Deferred tax asset, net of valuation allowance	42,345	$ 62,108
Income taxes receivable	$ 2,000	$ 1,400
U.S. statutory tax rate	35.00%	35.00%	35.00%
Carryforward limitation, 4 to 6 years
Income Tax Disclsoure [Line Items]
Foreign loss carryforwards	$ 600
Foreign Tax Authority | Her Majesty's Revenue and Customs (HMRC)
Income Tax Disclsoure [Line Items]
Deferred tax asset, net of valuation allowance	$ 2,100
Minimum
Income Tax Disclsoure [Line Items]
Carryforward period	8 years
Minimum | Carryforward limitation, 4 to 6 years
Income Tax Disclsoure [Line Items]
Carryforward period	4 years
Maximum | Carryforward limitation, 4 to 6 years
Income Tax Disclsoure [Line Items]
Carryforward period	6 years

Income Taxes - Net Deferred Tax

Income Taxes - Net Deferred Tax Assets and Liabilities (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Compensation and benefits	$ 23,080	$ 32,021
Depreciation and amortization	1,521	2,483
Cumulative translation adjustment	8,878	20,361
Operating loss carryforwards	10,133	4,944
Capital loss carryforwards	2,106	1,938
Unrealized loss on investments	61	0
Other financial accruals	2,047	2,299
Valuation allowances	(5,481)	(1,938)
Total deferred tax assets	42,345	62,108
Deferred tax liabilities:
Unrealized gain on investments	0	659
Other financial accruals	2,928	3,008
Total deferred tax liabilities	2,928	3,667
Net deferred tax asset	$ 39,417	$ 58,441

Income Taxes - Reconciliation o

Income Taxes - Reconciliation of Statutory U.S. Federal Income Tax Rate to Company's Effective Income Tax Rate (Details)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
U.S. statutory tax rate	35.00%	35.00%	35.00%
Increase related to state and local taxes, net of U.S. income tax benefit	(499.90%)	1.30%	4.70%
Benefits and taxes related to foreign operations	(2796.30%)	(6.20%)	0.70%
Accounting pronouncement for equity compensation including foreign	(486.20%)	0.00%	0.00%
Rate change to deferred items related to Tax Cuts and Jobs Act	(5193.70%)	0.00%	0.00%
Other	89.20%	0.80%	0.50%
Effective income tax rate	(8851.90%)	30.90%	40.90%

Regulatory - Additional Informa

Regulatory - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)
Regulatory Capital Requirements [Abstract]
Description of minimum net capital requirements	The greater of $5,000 or 1/15 of aggregate indebtedness
Minimum net capital requirements (greater than $5,000 or 1/15 of aggregate indebtedness)	$ 5,000
Minimum net capital requirements (greater than $5,000 or 1/15 of aggregate indebtedness)	6.67%
Net capital	$ 5,000,000	$ 7,300,000
Excess net capital	$ 4,000,000	$ 5,900,000
Aggregate indebtedness to net capital ratio	3.03	2.80

Business Information - Addition

Business Information - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2017USD ($)SegmentEntity	Dec. 31, 2016USD ($)Entity	Dec. 31, 2015
Segment Reporting Information [Line Items]
Number of business segments (segment) | Segment	1
United States
Segment Reporting Information [Line Items]
Long-lived assets | $	$ 36.6	$ 34.8
Revenue
Segment Reporting Information [Line Items]
Percentage of revenues from investments (less than)	1.00%
Revenue | Geographic Concentration Risk | United States
Segment Reporting Information [Line Items]
Percent of revenue per derived location	70.00%	59.00%	66.00%
Revenue | Geographic Concentration Risk | United Kingdom
Segment Reporting Information [Line Items]
Percent of revenue per derived location	15.00%	27.00%	20.00%
Advisory Services
Segment Reporting Information [Line Items]
Number of clients that accounted for more than 10% of total revenues (entity) | Entity	0	0

Business Information - Informat

Business Information - Information by Geographic Region, After Elimination of All Significant Inter-company Accounts and Transactions (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Segment Reporting Information [Line Items]
Total revenues	$ 66,900	$ 48,100	$ 67,300	$ 56,900	$ 101,600	$ 76,600	$ 90,500	$ 66,900	$ 239,182	$ 335,519	$ 261,560
Income (loss) before taxes	(1,700)	$ (10,300)	$ 9,600	$ 2,100	32,400	$ 19,200	$ 29,900	$ 6,500	(298)	87,881	43,295
Total assets	610,817				456,682				610,817	456,682	423,144
North America
Segment Reporting Information [Line Items]
Total revenues									169,502	206,673	172,582
Income (loss) before taxes									15,315	48,927	40,895
Total assets	426,799				266,975				426,799	266,975	261,077
Europe
Segment Reporting Information [Line Items]
Total revenues									47,441	110,229	63,875
Income (loss) before taxes									(10,547)	52,650	9,577
Total assets	48,195				64,467				48,195	64,467	38,409
Rest of World
Segment Reporting Information [Line Items]
Total revenues									22,239	18,617	25,103
Income (loss) before taxes									(5,066)	(13,696)	(7,177)
Total assets	$ 135,823				$ 125,240				$ 135,823	$ 125,240	$ 123,658

Subsequent Events (Details)

Subsequent Events (Details) - USD ($) $ / shares in Units, $ in Millions

Feb. 12, 2018

Feb. 06, 2018

Dec. 31, 2017

Sep. 30, 2017

Jun. 30, 2017

Mar. 31, 2017

Dec. 31, 2016

Sep. 30, 2016

Jun. 30, 2016

Mar. 31, 2016

Dec. 31, 2017

Dec. 31, 2016

Dec. 31, 2015

Subsequent Event [Line Items]

Dividends declared per common share (usd per share)

$ 0.05

$ 0.45

$ 0.45

$ 0.45

$ 0.45

$ 0.45

$ 0.45

$ 0.45

$ 1.40

$ 1.8

$ 1.80

Share repurchase program, September 2017 | Common stock

Subsequent Event [Line Items]

Authorized repurchase amount

$ 285

Remaining authorization under share repurchase plan

$ 219.2

$ 219.2

Subsequent event

Subsequent Event [Line Items]

Dividends declared per common share (usd per share)

$ 0.05

Dividend payable date

Mar. 21, 2018

Dividend record date

Mar. 7, 2018

Subsequent event | Share repurchase program, September 2017 | Common stock

Subsequent Event [Line Items]

Remaining authorization under share repurchase plan

$ 212.7

Increase (decrease) in stock repurchase program, authorization if the tender off is fully subscribed

$ 102.7

Number of business days before repurchase program will be implemented through other means

10 days

Subsequent event | Stock repurchase program, September 2017, modified Dutch auction | Common stock

Subsequent Event [Line Items]

Authorized repurchase amount

$ 110

Subsequent event | Stock repurchase program, September 2017, modified Dutch auction | Common stock | Minimum

Subsequent Event [Line Items]

Amount shareholders can offer to sell their shares, modified Dutch auction (in dollars per share)

$ 18.50

Subsequent event | Stock repurchase program, September 2017, modified Dutch auction | Common stock | Maximum

Subsequent Event [Line Items]

Incremental threshold in which shareholders can sell their shares, modified Dutch auction (in dollars per share)

$ 20.50

Supplemental Financial Inform77

Supplemental Financial Information Quarterly Results (unaudited) - Schedule of Unaudited Quarterly Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Selected Quarterly Financial Information [Abstract]
Total revenues	$ 66,900	$ 48,100	$ 67,300	$ 56,900	$ 101,600	$ 76,600	$ 90,500	$ 66,900	$ 239,182	$ 335,519	$ 261,560
Total operating expenses	63,900	57,500	56,900	54,000	68,400	56,500	59,800	59,700	232,282	244,411	215,787
Total operating income	3,000	(9,400)	10,400	2,900	33,200	20,100	30,700	7,200	6,900	91,108	45,773
Interest expense	4,700	900	800	800	800	900	800	700	7,198	3,227	2,478
Income (loss) before taxes	(1,700)	(10,300)	9,600	2,100	32,400	19,200	29,900	6,500	(298)	87,881	43,295
Provision (benefit) for taxes	24,500	(4,400)	3,300	2,900	8,700	6,100	10,200	2,100	26,353	27,119	17,697
Net income allocated to common stockholders	$ (26,200)	$ (5,900)	$ 6,300	$ (800)	$ 23,700	$ 13,100	$ 19,700	$ 4,400	$ (26,651)	$ 60,762	$ 25,598
Earnings (loss) per share:
Basic (usd per share)	$ (0.85)	$ (0.18)	$ 0.20	$ (0.02)	$ 0.74	$ 0.41	$ 0.62	$ 0.14	$ (0.83)	$ 1.90	$ 0.82
Diluted (usd per share)	(0.85)	(0.18)	0.20	(0.02)	0.74	0.41	0.62	0.14	(0.83)	1.89	0.82
Dividends declared per share (usd per share)	$ 0.05	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 1.40	$ 1.8	$ 1.80