Common Shares Issuable upon Conversion of Convertible Stock

No definition available.

Name:	ghl_CommonSharesIssuableUponConversionOfConvertibleStock
Namespace Prefix:	ghl_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Performance Stock, Value at Acquisition Date

+ References

No definition available.

+ Details

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Namespace Prefix:	ghl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Dividend equivalents paid on restricted stock units.

+ References

No definition available.

+ Details

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Namespace Prefix:	ghl_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Share Based Compensation Arrangement by Share Based Payment Award, Per Share Average Price of Shares Purchased

+ References

No definition available.

+ Details

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Namespace Prefix:	ghl_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:	ghl_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate dividends paid during the period for each share of common stock outstanding.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Article 3

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 505

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.3-04)

-URI http://asc.fasb.org/extlink&oid=27012166&loc=d3e187085-122770

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of shares converted in a noncash (or part noncash) transaction. Noncash is defined as transactions during a period that do not result in cash receipts or cash payments in the period. "Part noncash" refers to that portion of the transaction not resulting in cash receipts or cash payments in the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4332-108586

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 4

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4313-108586

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 50

-Paragraph 3

-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4304-108586

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(iii)(2)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of shares purchased on the open market during the period for issuance to employees under the plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Details

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Namespace Prefix:
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- Details

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- Details

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Equity - Additional Information (Detail) (USD $) In Millions, except Share data, unless otherwise specified	0 Months Ended	3 Months Ended		1 Months Ended
	Mar. 18, 2015	Mar. 31, 2015	Mar. 31, 2014	Apr. 30, 2013	Apr. 01, 2010	Apr. 01, 2015
Stockholders Equity Note [Line Items]
Dividends declared per common share (in USD per share)	$ 0.45	$ 0.45	$ 0.45
Restricted Stock Units Dividends Paid		$ 1.6ghl_RestrictedStockUnitsDividendsPaid	$ 1.6ghl_RestrictedStockUnitsDividendsPaid
Common Stock
Stockholders Equity Note [Line Items]
Repurchased shares for award (shares)		307,007	323,190
Average repurchase price of shares for award (USD per share)		$ 34.40	$ 52.06
Contingent Convertible Preferred Stock \| Caliburn Acquisition
Stockholders Equity Note [Line Items]
Conversion to common stock shares if revenue targets are achieved (shares)					1,099,877
Performance stock fair value at acquisition date					32.5
Contingent Convertible Preferred Stock \| Tranche One - Performance Stock \| Caliburn Acquisition
Stockholders Equity Note [Line Items]
Conversion of Stock (shares)				659,926
Contingent Convertible Preferred Stock \| Tranche Two - Performance Stock \| Caliburn Acquisition
Stockholders Equity Note [Line Items]
Conversion to common stock shares if revenue targets are achieved (shares)					439,951
Restricted Stock Units
Stockholders Equity Note [Line Items]
Restricted stock units vested and issued as common stock (shares)		731,251	822,312
Subsequent Event \| Contingent Convertible Preferred Stock \| Caliburn Acquisition
Stockholders Equity Note [Line Items]
Performance stock fair value at acquisition date						$ 14.4