Investments - Cost or Amortized Cost and Fair Value of Securities Available for Sale (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	$ 500,930	$ 426,568
Gross Unrealized Gains	866	514
Gross Unrealized Losses	(3,667)	(3,501)
Fair Value	498,129	423,581
Short-term Investments [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	100,033	50,000
Gross Unrealized Gains	12
Gross Unrealized Losses	(20)	(10)
Fair Value	100,025	49,990
U.S. Government Obligations and Agencies [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	99,290	120,627
Gross Unrealized Gains	71	38
Gross Unrealized Losses	(234)	(627)
Fair Value	99,127	120,038
Corporate Bonds [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	126,662	120,025
Gross Unrealized Gains	263	171
Gross Unrealized Losses	(276)	(364)
Fair Value	126,649	119,832
Mortgage-Backed and Asset-Backed Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	119,296	107,589
Fair Value	119,088	107,223
Mortgage-Backed and Asset-Backed Securities [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	119,296	107,589
Gross Unrealized Gains	328	136
Gross Unrealized Losses	(536)	(502)
Fair Value	119,088	107,223
Redeemable Preferred Stock [Member] \| Fixed Maturities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	9,650	6,700
Gross Unrealized Gains	156	165
Gross Unrealized Losses	(85)	(9)
Fair Value	9,721	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	6,617	331
Gross Unrealized Gains	2	4
Gross Unrealized Losses	(311)	(65)
Fair Value	6,308	270
Mutual Funds [Member] \| Equity Securities [Member]
Schedule Of Available For Sale Securities [Line Items]
Cost or Amortized Cost	34,382	21,296
Gross Unrealized Gains	30
Gross Unrealized Losses	(2,205)	(1,924)
Fair Value	$ 32,207	$ 19,372

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

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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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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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