Deferred Policy Acquisition Costs (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2017	Mar. 31, 2016
Insurance [Abstract]
Amortization of deferred policy acquisition costs	$ 22.6	$ 21.5

Amount of expense related to deferred policy acquisition costs.

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(7)(a))
-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 30
-Section 35
-Paragraph 11
-URI http://asc.fasb.org/extlink&oid=49177698&loc=d3e10157-158409

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 235
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-16(Column I))
-URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574960-122915

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 235
-Section S99
-Paragraph 3
-Subparagraph (SX 210.12-18(Column I))
-URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e575016-122915

Reference 5: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 45
-Paragraph 2
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6480726&loc=d3e6691-158385

Reference 6: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=35755530&loc=d3e11264-158415

Name:	us-gaap_DeferredPolicyAcquisitionCostAmortizationExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration