An additional amount of commitments that may be added to the aggregate balance with approval of the lenders.

No definition available.

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- Definition

Line of Credit Sublimit for Swingline Loans

+ References

No definition available.

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- Definition

Period of Annual Payments on Mortgages

+ References

No definition available.

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- Definition

Repayment Of Swingline Loans Period

+ References

No definition available.

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- Definition

Amount of the total principal payments made during the annual reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Balance Type:	debit
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- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
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- Definition

Description of the frequency of periodic payments (monthly, quarterly, annual).

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (SX 210.5-02.22(a)(1))
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- 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.

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- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (SX 210.5-02.22(a)(2))
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Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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-Subparagraph (SX 210.5-02.22(b))
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- Definition

The maximum amount of borrowing capacity under a line of credit that is available as of the balance sheet date for a specific purpose other than for financing goods acquired for inventory or imminent delivery to a customer.

+ References

No definition available.

+ Details

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- Definition

Date the credit facility first became available, in CCYY-MM-DD format.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
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Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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- Definition

Amount of cash inflow from issuance of long-term debt classified as other.

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Debt and Financing Arrangements (Narrative) (Details) SFr in Millions, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2016 CHF (SFr)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2016 CHF (SFr)	Nov. 12, 2014 USD ($)
Debt Instrument [Line Items]
Principal amount	$ 800.0		$ 1,300.0
Proceeds from other long-term debt	0.0		4.0	$ 19.2
Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Proceeds from other long-term debt			0.0	$ 0.0
2006 Senior notes due 2016 \| Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Principal amount	$ 500.0
Debt Instrument, interest rate	7.50%				7.50%
Senior Notes, maturity date	Aug. 01, 2016	Aug. 01, 2016
Senior Notes, frequency of periodic payment	semi-annually	semi-annually
2010 Senior notes due 2020 \| Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Principal amount	$ 300.0
Debt Instrument, interest rate	5.50%				5.50%
Senior Notes, maturity date	Nov. 15, 2020	Nov. 15, 2020
2015 Senior notes Due 2025 \| Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Principal amount	$ 500.0
Debt Instrument, interest rate	4.35%				4.35%
Senior Notes, maturity date	Oct. 29, 2025	Oct. 29, 2025
Senior Notes, frequency of periodic payment	semi-annually	semi-annually
$900,000 secured letter of credit facility - uncommitted
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 900.0		1,000.0
$900,000 secured letter of credit facility - uncommitted \| Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 900.0		1,000.0
$800,000 secured letter of credit facility [Member] \| Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Line of Credit Facility, Initiation Date	Nov. 27, 2007	Nov. 27, 2007
Line of Credit Facility, Maximum Borrowing Capacity	$ 800.0
Debt instrument term	5 years	5 years
$400,000 secured letter of credit facility (pre-amendment) \| Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 400.0
$400,000 unsecured letter of credit facility \| Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 400.0
$150,000 secured letter of credit facility \| Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Line of Credit Facility, Initiation Date	Jun. 07, 2012	Jun. 07, 2012
Line of Credit Facility, Maximum Borrowing Capacity	$ 150.0		$ 150.0			$ 450.0
Debt instrument term	4 years	4 years
Line of Credit Facility, Capacity Available for Specific Purpose Other than for Trade Purchases	$ 150.0
Additional commitments subject to lender approval	150.0
$200,000 unsecured revolving credit facility \| Allied World Bermuda (Subsidiary Issuer)
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 200.0
Debt instrument term	5 years	5 years
Additional commitments subject to lender approval	$ 150.0
Line of Credit Sublimit for Swingline Loans	$ 25.0
Repayment Of Swingline Loans Period	10 days	10 days
Switzerland
Debt Instrument [Line Items]
Number of annual principal payments required	19 years	19 years
Switzerland \| Swiss office building mortgage
Debt Instrument [Line Items]
Debt Instrument, interest rate	3.20%				3.20%
Proceeds from other long-term debt	$ 14.2	SFr 14.0
Additional borrowing capacity	4.0				SFr 4.0
Annual principal payment	$ 0.3				SFr 0.3
Debt instrument term	20 years	20 years
Switzerland \| Swiss office building credit facility
Debt Instrument [Line Items]
Debt Instrument, interest rate	2.50%				2.50%
Line of Credit Facility, Maximum Borrowing Capacity	$ 5.1				SFr 5.0
Debt instrument term	3 years	3 years