Amount, before accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
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The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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- Definition

Financial instruments issued by insurance entities (surplus notes) that are includable in surplus for statutory accounting purposes as prescribed or permitted by state laws and regulations that are liabilities of the issuer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 470
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6486086&loc=d3e24387-158525

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- Definition

Percentage of par value of policy reinsured.

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Summary of Significant Accounting Policies (Basis of Presentation) (Details) - USD ($) $ in Millions	Mar. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 31, 2012
Basis of Presentation
Debt Issuance Cost	$ 1.8
OneBeacon Ltd.
Basis of Presentation
Ownership interest (as a percent)	75.70%	76.10%
HG Global
Basis of Presentation
Noncontrolling equity percentage	3.10%	3.10%
Surplus Notes				$ 503.0
Percentage of par value of policy reinsured	15.00%
OneBeacon [Member]
Basis of Presentation
Noncontrolling equity percentage	24.30%	23.90%
Debt Issuance Cost			$ 1.9
Preferred Stock \| HG Global
Basis of Presentation
Noncontrolling equity percentage		96.90%
Ownership interest (as a percent)	96.90%
Common Stock \| HG Global
Basis of Presentation
Noncontrolling equity percentage		88.40%
Ownership interest (as a percent)	88.40%