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Reinsurance (Ceded Premiums and Losses Related to Flood Operations) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Percentage of unpaid NFIP claims ceded by federal government	100.00%
Ceded premiums written	$ (368,750)	$ (357,463)	$ (369,296)
Ceded premiums earned	(363,357)	(363,567)	(365,302)
Ceded losses and loss expenses incurred	(348,267)	(143,327)	(183,550)
National Flood Insurance Program [Member]
Ceded premiums written	(232,245)	(228,907)	(237,718)
Ceded premiums earned	(227,882)	(233,940)	(234,224)
Ceded losses and loss expenses incurred	$ (239,891)	$ (62,078)	$ (57,323)

X

- Definition

Percentage of unpaid NFIP claims ceded by federal government

+ References

No definition available.

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- Definition

Amount of earned premiums ceded to other entities.

+ 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)(2)
-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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-Name Accounting Standards Codification
-Topic 944
-SubTopic 235
-Section S99
-Paragraph 2
-Subparagraph (SX 210.12-17)
-URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574992-122915

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Amount of written premiums ceded to other entities.

+ References

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

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-Publisher FASB
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-Subparagraph (b)(3)
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Amount of reduction of provision for policy benefits and costs incurred for policies ceded.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 20
-Section 50
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=6480758&loc=d3e6811-158387

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