Summary of Significant Accounting Policies - Summary of Investments Held to Maturity (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Gain (Loss) on Investments [Line Items]
Amortized Cost	$ 17,483	$ 15,987
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	(33)	(23)
Fair Value	17,450	15,964
Held-to-maturity Securities, Noncurrent	5,039	4,015
Current Assets [Member]
Gain (Loss) on Investments [Line Items]
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	(16)	(7)
Fair Value	12,428	11,965
Non Current Assets [Member]
Gain (Loss) on Investments [Line Items]
Gross Unrealized Gain	0	0
Gross Unrealized (Loss)	(17)	(16)
Fair Value	$ 5,022	$ 3,999