Investments - Summarized Fair Value and Gross Unrealized Losses on Securities Available for Sale (Detail) $ in Thousands	Mar. 31, 2016 USD ($) Security	Dec. 31, 2015 USD ($) Security
Schedule Of Available For Sale Securities [Line Items]
Less than 12 months, Number of issues \| Security	58	174
Less than 12 months, Fair value	$ 123,085	$ 359,017
Less than 12 months, Unrealized losses	$ (1,301)	$ (3,143)
12 months or longer, Number of issues \| Security	19	17
12 months or longer, Fair value	$ 32,630	$ 30,080
12 months or longer, Unrealized losses	$ (3,438)	$ (4,078)
U.S. Government Obligations and Agencies [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 months, Number of issues \| Security	2	10
Less than 12 months, Fair value	$ 28,934	$ 121,912
Less than 12 months, Unrealized losses	$ (26)	$ (690)
12 months or longer, Number of issues \| Security	2	2
12 months or longer, Fair value	$ 3,506	$ 3,429
12 months or longer, Unrealized losses	$ (64)	$ (177)
Corporate Bonds [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 months, Number of issues \| Security	28	101
Less than 12 months, Fair value	$ 24,139	$ 90,717
Less than 12 months, Unrealized losses	$ (304)	$ (927)
12 months or longer, Number of issues \| Security	7	6
12 months or longer, Fair value	$ 7,826	$ 4,789
12 months or longer, Unrealized losses	$ (145)	$ (114)
Mortgage-Backed and Asset-Backed Securities [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 months, Number of issues \| Security	17	51
Less than 12 months, Fair value	$ 32,977	$ 118,743
Less than 12 months, Unrealized losses	$ (198)	$ (974)
12 months or longer, Number of issues \| Security	5	6
12 months or longer, Fair value	$ 12,486	$ 13,902
12 months or longer, Unrealized losses	$ (118)	$ (291)
Redeemable Preferred Stock [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 months, Number of issues \| Security	5	5
Less than 12 months, Fair value	$ 2,149	$ 764
Less than 12 months, Unrealized losses	$ (9)	$ (29)
12 months or longer, Number of issues \| Security	2
12 months or longer, Fair value	$ 257
12 months or longer, Unrealized losses	$ (5)
Other [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 months, Number of issues \| Security		1
Less than 12 months, Fair value		$ 4,999
Less than 12 months, Unrealized losses		$ (1)
Common Stock [Member] \| Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 months, Number of issues \| Security	1	3
Less than 12 months, Fair value	$ 67	$ 8,690
Less than 12 months, Unrealized losses	$ (13)	$ (148)
12 months or longer, Number of issues \| Security	2	2
12 months or longer, Fair value	$ 119	$ 93
12 months or longer, Unrealized losses	$ (96)	$ (96)
Mutual Funds [Member] \| Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Less than 12 months, Number of issues \| Security	5	3
Less than 12 months, Fair value	$ 34,819	$ 13,192
Less than 12 months, Unrealized losses	$ (751)	$ (374)
12 months or longer, Number of issues \| Security	1	1
12 months or longer, Fair value	$ 8,436	$ 7,867
12 months or longer, Unrealized losses	$ (3,010)	$ (3,400)

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.

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=27724398&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=27724398&loc=d3e27337-111563

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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 less than twelve months.

+ References

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- Definition

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=27724398&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=27724398&loc=d3e27290-111563

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+ 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)(1)
-URI http://asc.fasb.org/extlink&oid=27724398&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=27724398&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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