Fair Value Measurements - Additional Information (Details)	3 Months Ended
	Mar. 31, 2016 USD ($) Security	Mar. 31, 2015 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between Levels 1 and 2	$ 0	$ 0
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of securities | Security	1
Asset-Backed | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between Levels 2 and 3	$ 26,700,000
Other Investments | Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Transfers between Levels 3 and 2	$ 97,800,000