Investments - Cost or Amortized Cost and Fair Value of Securities Available for Sale (Detail) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	$ 614,968	$ 489,846
Gross Unrealized Gains	7,153	693
Gross Unrealized Losses	(3,764)	(7,221)
Fair Value	618,357	483,318
Short-term Investments [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	5,000	25,011
Gross Unrealized Gains	4	10
Fair Value	5,004	25,021
U.S. Government Obligations and Agencies and Municipal Securities [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	144,716
Gross Unrealized Gains	1,918
Gross Unrealized Losses	(55)
Fair Value	146,579
Corporate Bonds [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	186,111	126,421
Gross Unrealized Gains	2,674	137
Gross Unrealized Losses	(216)	(1,041)
Fair Value	188,569	125,517
Mortgage-Backed and Asset-Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	230,694	151,328
Fair Value	232,231	150,160
Mortgage-Backed and Asset-Backed Securities [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	230,694	151,328
Gross Unrealized Gains	1,770	97
Gross Unrealized Losses	(233)	(1,265)
Fair Value	232,231	150,160
Redeemable Preferred Stock [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	9,732	9,665
Gross Unrealized Gains	705	429
Gross Unrealized Losses	(6)	(29)
Fair Value	10,431	10,065
Common Stock [Member] \| Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	3,224	10,991
Gross Unrealized Gains		15
Gross Unrealized Losses	(138)	(244)
Fair Value	3,086	10,762
Mutual Funds [Member] \| Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	35,491	35,221
Gross Unrealized Gains	82	5
Gross Unrealized Losses	(3,116)	(3,774)
Fair Value	$ 32,457	31,452
U.S. Government Obligations and Agencies [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost		126,209
Gross Unrealized Losses		(867)
Fair Value		125,342
Other [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost		5,000
Gross Unrealized Losses		(1)
Fair Value		$ 4,999

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.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
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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
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-Section S99
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