Investments - Cost or Amortized Cost and Fair Value of Securities Available for Sale (Detail) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	$ 543,513	$ 426,568
Gross Unrealized Gains	2,136	514
Gross Unrealized Losses	(6,230)	(3,501)
Fair Value	539,419	423,581
Short-term Investments [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	75,022	50,000
Gross Unrealized Gains	3
Gross Unrealized Losses	(2)	(10)
Fair Value	75,023	49,990
U.S. Government Obligations and Agencies [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	135,774	120,627
Gross Unrealized Gains	517	38
Gross Unrealized Losses	(201)	(627)
Fair Value	136,090	120,038
Corporate Bonds [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	128,357	120,025
Gross Unrealized Gains	412	171
Gross Unrealized Losses	(649)	(364)
Fair Value	128,120	119,832
Mortgage-Backed and Asset-Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	138,482	107,589
Fair Value	138,685	107,223
Mortgage-Backed and Asset-Backed Securities [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	138,482	107,589
Gross Unrealized Gains	527	136
Gross Unrealized Losses	(324)	(502)
Fair Value	138,685	107,223
Redeemable Preferred Stock [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	9,734	6,700
Gross Unrealized Gains	201	165
Gross Unrealized Losses	(65)	(9)
Fair Value	9,870	6,856
Other [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	5,000
Gross Unrealized Gains	4
Fair Value	5,004
Common Stock [Member] \| Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	16,545	331
Gross Unrealized Gains	472	4
Gross Unrealized Losses	(1,274)	(65)
Fair Value	15,743	270
Mutual Funds [Member] \| Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	34,599	21,296
Gross Unrealized Losses	(3,715)	(1,924)
Fair Value	$ 30,884	$ 19,372

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

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-Publisher FASB

-Name Accounting Standards Codification

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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.

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