Premiums written for all insurance and reinsurance contracts, after adding premiums assumed from other insurers and subtracting any amounts ceded to another insurer.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 17

-Article 12

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 113

-Paragraph 27

-Subparagraph a, b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 3: 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

Name:	us-gaap_PremiumsWrittenNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

Subsequent Event (Details) (USD $) In Millions, unless otherwise specified	0 Months Ended	12 Months Ended
	Jan. 02, 2013	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Subsequent Event [Line Items]
Premiums written, net		$ 2,126.9	$ 1,978.4	$ 2,033.5
Essentia \| Subsequent Event
Subsequent Event [Line Items]
Gain on sale of disposition, before tax	23
Gain (loss) on sale of discontinued operation, net of tax	15
Premiums written, net		$ 179.7	$ 166.6	$ 153.0
Premiums written, percentage of total		8.00%