v2.4.0.6
Fair Value Measurement of Financial Assets and Financial Liabilities on Recurring Basis (Detail) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2012
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets $ 2,052,226
Fair Value of liabilities 297,819
U.S. treasury securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 48,341
U.S. government agencies
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 46,305
Municipal bonds
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 265,011
Commercial mortgage backed securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 10,209
Agency, residential mortgage backed securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 332,027
Non-agency, residential mortgage backed securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 6,759
Equity securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 18,318
Short term investments
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 485
Other investments
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 14,324
Life settlement contracts
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 171,476
Equity securities sold but not yet purchased, market
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 43
Fixed maturity securities sold but not yet purchased , market
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 57,155
Securities sold under agreements to repurchase, at contract value
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 226,098
Life settlement contract profit commission
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 9,550
Derivatives
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 4,973
Corporate Bonds | Finance
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 773,474
Corporate Bonds | Industrial
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 330,269
Corporate Bonds | Utilities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 35,228
Fair Value, Inputs, Level 1
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 67,144
Fair Value of liabilities 57,198
Fair Value, Inputs, Level 1 | U.S. treasury securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 48,341
Fair Value, Inputs, Level 1 | U.S. government agencies
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 1 | Municipal bonds
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 1 | Finance
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 1 | Industrial
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 1 | Utilities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 1 | Commercial mortgage backed securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 1 | Agency, residential mortgage backed securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 1 | Non-agency, residential mortgage backed securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 1 | Equity securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 18,318
Fair Value, Inputs, Level 1 | Short term investments
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 485
Fair Value, Inputs, Level 1 | Other investments
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 1 | Life settlement contracts
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 1 | Equity securities sold but not yet purchased, market
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 43
Fair Value, Inputs, Level 1 | Fixed maturity securities sold but not yet purchased , market
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 57,155
Fair Value, Inputs, Level 1 | Securities sold under agreements to repurchase, at contract value
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 0
Fair Value, Inputs, Level 1 | Life settlement contract profit commission
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 0
Fair Value, Inputs, Level 1 | Derivatives
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 0
Fair Value, Inputs, Level 2
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 1,799,282
Fair Value of liabilities 231,071
Fair Value, Inputs, Level 2 | U.S. treasury securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 2 | U.S. government agencies
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 46,305
Fair Value, Inputs, Level 2 | Municipal bonds
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 265,011
Fair Value, Inputs, Level 2 | Commercial mortgage backed securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 10,209
Fair Value, Inputs, Level 2 | Agency, residential mortgage backed securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 332,027
Fair Value, Inputs, Level 2 | Non-agency, residential mortgage backed securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 6,759
Fair Value, Inputs, Level 2 | Equity securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 2 | Short term investments
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 2 | Other investments
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 2 | Life settlement contracts
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 2 | Equity securities sold but not yet purchased, market
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 0
Fair Value, Inputs, Level 2 | Securities sold under agreements to repurchase, at contract value
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 226,098
Fair Value, Inputs, Level 2 | Life settlement contract profit commission
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 0
Fair Value, Inputs, Level 2 | Derivatives
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 4,973
Fair Value, Inputs, Level 2 | Corporate Bonds | Finance
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 773,474
Fair Value, Inputs, Level 2 | Corporate Bonds | Industrial
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 330,269
Fair Value, Inputs, Level 2 | Corporate Bonds | Utilities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 35,228
Fair Value, Inputs, Level 3
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 185,800
Fair Value of liabilities 9,550
Fair Value, Inputs, Level 3 | U.S. treasury securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 3 | U.S. government agencies
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 3 | Municipal bonds
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 3 | Finance
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 3 | Industrial
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 3 | Utilities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 3 | Commercial mortgage backed securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 3 | Agency, residential mortgage backed securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 3 | Non-agency, residential mortgage backed securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 3 | Equity securities
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 3 | Short term investments
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 0
Fair Value, Inputs, Level 3 | Other investments
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 14,324
Fair Value, Inputs, Level 3 | Life settlement contracts
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair value of assets 171,476
Fair Value, Inputs, Level 3 | Equity securities sold but not yet purchased, market
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 0
Fair Value, Inputs, Level 3 | Fixed maturity securities sold but not yet purchased , market
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 0
Fair Value, Inputs, Level 3 | Securities sold under agreements to repurchase, at contract value
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 0
Fair Value, Inputs, Level 3 | Life settlement contract profit commission
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities 9,550
Fair Value, Inputs, Level 3 | Derivatives
 
Fair Value, Assets and Liabilities Measured on Recurring Basis [Line Items]  
Fair Value of liabilities $ 0