Investments - Cost or Amortized Cost and Fair Value of Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	$ 638,865	$ 650,575
Gross Unrealized Gains	2,494	1,201
Gross Unrealized Losses	(6,105)	(11,610)
Fair Value	635,254	640,166
Mortgage-Backed and Asset-Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	219,321	216,679
Fair Value	218,098	214,776
Fixed Maturities [Member] \| U.S. Government Obligations and Agencies [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	55,519	74,937
Gross Unrealized Gains	21
Gross Unrealized Losses	(524)	(670)
Fair Value	55,016	74,267
Fixed Maturities [Member] \| Corporate Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	215,455	192,328
Gross Unrealized Gains	883	402
Gross Unrealized Losses	(507)	(1,300)
Fair Value	215,831	191,430
Fixed Maturities [Member] \| Mortgage-Backed and Asset-Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	219,321	216,679
Gross Unrealized Gains	110	135
Gross Unrealized Losses	(1,333)	(2,038)
Fair Value	218,098	214,776
Fixed Maturities [Member] \| Municipal Bonds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	106,926	94,794
Gross Unrealized Gains	706	130
Gross Unrealized Losses	(1,342)	(3,727)
Fair Value	106,290	91,197
Fixed Maturities [Member] \| Redeemable Preferred Stock [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	13,336	12,723
Gross Unrealized Gains	631	125
Gross Unrealized Losses	(23)	(157)
Fair Value	13,944	12,691
Equity Securities [Member] \| Common Stock [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	5,992	214
Gross Unrealized Losses	(309)	(121)
Fair Value	5,683	93
Equity Securities [Member] \| Mutual Funds [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	22,316	53,900
Gross Unrealized Gains	143	407
Gross Unrealized Losses	(2,067)	(3,597)
Fair Value	$ 20,392	50,710
Short-term Investments [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost		5,000
Gross Unrealized Gains		2
Fair Value		$ 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=75030427&loc=d3e22054-111558

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 5
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-URI http://asc.fasb.org/extlink&oid=82897076&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82896770&loc=d3e26610-111562

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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
-SubTopic 10
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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
-Name Accounting Standards Codification
-Topic 320
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+ References

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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