Reinsurance Balances Recoverable - Summary of Provisions for Uncollectible Reinsurance Balances Recoverable by Rating of Reinsurer (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Effects of Reinsurance [Line Items]
Gross	$ 1,541,840	$ 1,684,331
Provisions for Bad Debt	196,725	210,327
Net	$ 1,345,115	$ 1,474,004
Provisions as a % of Gross	12.80%	12.50%
Reinsurers rated A- or above
Effects of Reinsurance [Line Items]
Gross	$ 983,600	$ 1,051,927
Provisions for Bad Debt	39,264	46,969
Net	$ 944,336	$ 1,004,958
Provisions as a % of Gross	4.00%	4.50%
Secured \| Reinsurers rated below A-
Effects of Reinsurance [Line Items]
Gross	$ 338,795	$ 388,399
Provisions for Bad Debt	0	0
Net	$ 338,795	$ 388,399
Provisions as a % of Gross	0.00%	0.00%
Unsecured \| Reinsurers rated below A-
Effects of Reinsurance [Line Items]
Gross	$ 219,445	$ 244,005
Provisions for Bad Debt	157,461	163,358
Net	$ 61,984	$ 80,647
Provisions as a % of Gross	71.80%	66.90%

Percentage of Reinsurance Recoverables Allowance to Reinsurance Recoverables Gross

No definition available.

Name:	esgr_PercentageofReinsuranceRecoverablesAllowancetoReinsuranceRecoverablesGross
Namespace Prefix:	esgr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_EffectsOfReinsuranceLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of valuation allowance for reinsurance recoverables. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

+ References

No definition available.

+ Details

Name:	us-gaap_ReinsuranceRecoverablesAllowance
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount before valuation allowance recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, premium paid, policy benefits and policy reserves.

+ References

No definition available.

+ Details

Name:	us-gaap_ReinsuranceRecoverablesGross
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after valuation allowance, recoverable under reinsurance contracts. Examples include, but are not limited to, settled and unsettled claims, incurred but not reported losses, loss adjustment expense, policy benefits and policy reserves. Excludes premiums paid under reinsurance contracts.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 45
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6485522&loc=d3e21412-158489

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 310
-Section 45
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6485522&loc=d3e21409-158489

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6824-158387

+ Details

Name:	us-gaap_ReinsuranceRecoverablesOnPaidAndUnpaidLosses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_CededCreditRiskAxis=esgr_ReinsurersRatedAMinusOrAboveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CededCreditRiskCollateralizationAxis=us-gaap_CededCreditRiskSecuredMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CededCreditRiskAxis=esgr_ReinsurersRatedBelowAMinusMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CededCreditRiskCollateralizationAxis=us-gaap_CededCreditRiskUnsecuredMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: