v3.3.1.900
Fair Value Measurements - Financial Instruments Not Measured at Fair Value (Details) - USD ($)
$ in Thousands
Dec. 31, 2015
Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial Assets $ 4,118,875 $ 3,469,475
Carrying Value | Significant Other Observable Inputs (Level 2)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial Assets 607,843 0
Financial Liabilities 360,000 360,000
Carrying Value | Senior Notes | Significant Other Observable Inputs (Level 2) | MHNA - 8.25%    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial Liabilities $ 107,500 $ 107,500
Stated interest rate 8.25% 8.25%
Carrying Value | Senior Notes | Significant Other Observable Inputs (Level 2) | MHNB - 8.00%    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial Liabilities $ 100,000 $ 100,000
Stated interest rate 8.00% 8.00%
Carrying Value | Senior Notes | Significant Other Observable Inputs (Level 2) | MHNC - 7.75%    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial Liabilities $ 152,500 $ 152,500
Stated interest rate 7.75% 7.75%
Fair Value | Significant Other Observable Inputs (Level 2)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial Assets $ 598,975 $ 0
Financial Liabilities 381,208 381,727
Fair Value | Senior Notes | Significant Other Observable Inputs (Level 2) | MHNA - 8.25%    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial Liabilities 110,424 113,391
Fair Value | Senior Notes | Significant Other Observable Inputs (Level 2) | MHNB - 8.00%    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial Liabilities 105,328 106,320
Fair Value | Senior Notes | Significant Other Observable Inputs (Level 2) | MHNC - 7.75%    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial Liabilities 165,456 162,016
Held-to-maturity Securities | Corporate bonds | Carrying Value | Significant Other Observable Inputs (Level 2)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial Assets 607,843 0
Held-to-maturity Securities | Corporate bonds | Fair Value | Significant Other Observable Inputs (Level 2)    
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]    
Financial Assets $ 598,975 $ 0