Investments - Schedule of Unrealized Loss on Investments (Details) $ in Thousands	Jun. 30, 2017 USD ($) security	Dec. 31, 2016 USD ($) security	Sep. 30, 2016 USD ($) security
Less Than Twelve Months
Number of securities \| security	513	646
Gross unrealized losses	$ 2,597	$ 5,898
Fair value	$ 304,287	$ 344,434
Twelve Months or More
Number of securities \| security	38	25
Gross unrealized losses	$ 401	$ 236
Fair value	$ 12,733	$ 3,122
U.S. Government and Agency Securities
Less Than Twelve Months
Number of securities \| security	168	186
Gross unrealized losses	$ 1,154	$ 1,893
Fair value	$ 102,522	$ 111,216
Twelve Months or More
Number of securities \| security	21	0
Gross unrealized losses	$ 189	$ 0
Fair value	$ 5,858	$ 0
States, Municipalities and Political Subdivisions
Less Than Twelve Months
Number of securities \| security	102	201
Gross unrealized losses	$ 483	$ 2,551
Fair value	$ 74,197	$ 136,360
Twelve Months or More
Number of securities \| security	4	0
Gross unrealized losses	$ 64	$ 0
Fair value	$ 4,717	$ 0
Public Utilities
Less Than Twelve Months
Number of securities \| security	12	8
Gross unrealized losses	$ 46	$ 73
Fair value	$ 3,080	$ 2,222
Twelve Months or More
Number of securities \| security	0	0
Gross unrealized losses	$ 0	$ 0
Fair value	$ 0	$ 0
Corporate Securities
Less Than Twelve Months
Number of securities \| security	195	215
Gross unrealized losses	$ 601	$ 1,100
Fair value	$ 83,816	$ 88,605
Twelve Months or More
Number of securities \| security	1	1
Gross unrealized losses	$ 17	$ 26
Fair value	$ 1,025	$ 1,021
Asset-backed Securities
Less Than Twelve Months
Number of securities \| security	19
Gross unrealized losses	$ 7
Fair value	$ 13,848
Twelve Months or More
Number of securities \| security	0
Gross unrealized losses	$ 0
Fair value	$ 0
Redeemable Preferred Stocks
Less Than Twelve Months
Number of securities \| security	0	7
Gross unrealized losses	$ 0	$ 62
Fair value	$ 0	$ 764
Twelve Months or More
Number of securities \| security	3	0
Gross unrealized losses	$ 55	$ 0
Fair value	$ 310	$ 0
Fixed Maturities
Less Than Twelve Months
Number of securities \| security	496	617
Gross unrealized losses	$ 2,291	$ 5,679
Fair value	$ 277,463	$ 339,167
Twelve Months or More
Number of securities \| security	29	1
Gross unrealized losses	$ 325	$ 26
Fair value	$ 11,910	$ 1,021
Public Utilities
Less Than Twelve Months
Number of securities \| security	5
Gross unrealized losses	$ 22
Fair value	$ 594
Twelve Months or More
Number of securities \| security	5
Gross unrealized losses	$ 27
Fair value	$ 381
Common Stock
Less Than Twelve Months
Number of securities \| security	11	16
Gross unrealized losses	$ 61	$ 140
Fair value	$ 1,463	$ 2,450
Twelve Months or More
Number of securities \| security	4	17
Gross unrealized losses	$ 49	$ 179
Fair value	$ 442	$ 1,732
Nonredeemable Preferred Stocks
Less Than Twelve Months
Number of securities \| security		12
Gross unrealized losses		$ 52
Fair value		$ 1,830
Twelve Months or More
Number of securities \| security		7
Gross unrealized losses		$ 31
Fair value		$ 369
Equity Securities
Less Than Twelve Months
Number of securities \| security	17	28
Gross unrealized losses	$ 306	$ 192
Fair value	$ 26,824	$ 4,280
Twelve Months or More
Number of securities \| security	9	24
Gross unrealized losses	$ 76	$ 210
Fair value	$ 823	$ 2,101
Other Long-term Investments
Less Than Twelve Months
Number of securities \| security		1
Gross unrealized losses		$ 27
Fair value		$ 987
Twelve Months or More
Number of securities \| security		0
Gross unrealized losses		$ 0
Fair value		$ 0
Mutual Fund
Less Than Twelve Months
Number of securities \| security			1
Gross unrealized losses			$ 223
Fair value			$ 24,767
Twelve Months or More
Number of securities \| security			0
Gross unrealized losses			$ 0
Fair value			$ 0

Available For Sale Securities Continuous Unrealized Loss Position Less Than Twelve Months [Abstract]

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Available For Sale Securities Continuous Unrealized Loss Position Twelve Months or More [Abstract]

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- Definition

Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for twelve months or longer.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

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Amount of accumulated unrealized loss on investments in debt and equity securities classified as available-for-sale that have been in a continuous loss position for less than twelve months.

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This item represents the aggregate fair value of investments in debt and equity securities categorized neither as held-to-maturity nor trading securities that have been in a continuous unrealized loss position for less than twelve months.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27290-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 7
-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27337-111563

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Number of investment positions in available-for-sale investments in a continuous unrealized loss position for less than one year or normal operating cycle, if longer, for which an other-than-temporary impairment (OTTI) has not been recognized in the income statement.

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