Independent Insurance Agencies and Brokerages

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- Definition

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

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- Definition

The number of states the entity operates in as of the balance sheet date.

+ References

No definition available.

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- Definition

Amount, after premiums ceded to other entities and premiums assumed by the entity, of property and casualty premiums earned.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 225
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-04.1)
-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 50
-Paragraph 1
-Subparagraph (b),(c)
-URI http://asc.fasb.org/extlink&oid=6486672&loc=d3e27261-158547

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 605
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6486662&loc=d3e27175-158546

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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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Segment Information - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($) state Entity	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)
Segment Reporting Information [Line Items]
Net premiums earned \| $	$ 22,474.0	$ 19,899.1	$ 18,398.5
Depreciation \| $	$ 137.4	103.7	97.1
Commercial Lines Segment
Segment Reporting Information [Line Items]
Number of states \| state	49
Operating Segments \| Personal Lines Segment \| Agency Channel \| Lower Limit
Segment Reporting Information [Line Items]
Independent insurance agencies and brokerages \| Entity	35,000
Australia
Segment Reporting Information [Line Items]
Net premiums earned \| $	$ 20.2	$ 15.9	$ 17.1
Residential Insurance [Member] \| Property Segment
Segment Reporting Information [Line Items]
Number of states \| state	38
National Flood Insurance Program [Member] \| Property Segment
Segment Reporting Information [Line Items]
Number of states \| state	40