Investments - Schedule of Investment in Unrealized Loss Position (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Schedule of Available for Sale Securities [Line Items]
Fair Value, Less than 12 Months	$ 177,878	$ 109,370
Gross Unrealized Losses, Less than 12 Months	(258)	(94)
Total Fair Value	177,878	109,370
Total Gross Unrealized Losses	(258)	(94)
U.S. Government Securities
Schedule of Available for Sale Securities [Line Items]
Fair Value, Less than 12 Months	48,445	22,355
Gross Unrealized Losses, Less than 12 Months	(59)	(12)
Total Fair Value	48,445	22,355
Total Gross Unrealized Losses	(59)	(12)
U.S. Government Agency Securities
Schedule of Available for Sale Securities [Line Items]
Fair Value, Less than 12 Months	71,861	27,348
Gross Unrealized Losses, Less than 12 Months	(78)	(20)
Total Fair Value	71,861	27,348
Total Gross Unrealized Losses	(78)	(20)
Non-U.S. Government Securities
Schedule of Available for Sale Securities [Line Items]
Fair Value, Less than 12 Months	5,001
Gross Unrealized Losses, Less than 12 Months	(1)
Total Fair Value	5,001
Total Gross Unrealized Losses	(1)
Corporate Debt Securities
Schedule of Available for Sale Securities [Line Items]
Fair Value, Less than 12 Months	52,571	59,667
Gross Unrealized Losses, Less than 12 Months	(120)	(62)
Total Fair Value	52,571	59,667
Total Gross Unrealized Losses	$ (120)	$ (62)