Investments - Cost or Amortized Cost and Fair Value of Securities Available for Sale (Detail) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	$ 659,383	$ 650,575
Gross Unrealized Gains	2,641	1,201
Gross Unrealized Losses	(9,062)	(11,610)
Fair Value	652,962	640,166
Mortgage-Backed and Asset-Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	215,670	216,679
Fair Value	214,001	214,776
Fixed Maturities [Member] \| U.S. Government Obligations and Agencies [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	78,055	74,937
Gross Unrealized Gains	1
Gross Unrealized Losses	(587)	(670)
Fair Value	77,469	74,267
Fixed Maturities [Member] \| Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	194,289	192,328
Gross Unrealized Gains	727	402
Gross Unrealized Losses	(975)	(1,300)
Fair Value	194,041	191,430
Fixed Maturities [Member] \| Mortgage-Backed and Asset-Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	215,670	216,679
Gross Unrealized Gains	128	135
Gross Unrealized Losses	(1,797)	(2,038)
Fair Value	214,001	214,776
Fixed Maturities [Member] \| Municipal Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	100,762	94,794
Gross Unrealized Gains	307	130
Gross Unrealized Losses	(3,177)	(3,727)
Fair Value	97,892	91,197
Fixed Maturities [Member] \| Redeemable Preferred Stock [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	13,777	12,723
Gross Unrealized Gains	524	125
Gross Unrealized Losses	(29)	(157)
Fair Value	14,272	12,691
Equity Securities [Member] \| Common Stock [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	214	214
Gross Unrealized Losses	(119)	(121)
Fair Value	95	93
Equity Securities [Member] \| Mutual Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	51,616	53,900
Gross Unrealized Gains	953	407
Gross Unrealized Losses	(2,378)	(3,597)
Fair Value	50,191	50,710
Short-term Investments [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	5,000	5,000
Gross Unrealized Gains	1	2
Fair Value	$ 5,001	$ 5,002

Amount of investment in debt and equity securities categorized neither as held-to-maturity nor trading.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 25
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
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-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
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Amount before tax of unrealized gain in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
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Amount before tax of unrealized loss in accumulated other comprehensive income (AOCI) on investments in debt and equity securities classified as available-for-sale.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
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