Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance			$ 673,447
Other comprehensive income	$ 55	$ 1,200	1	$ 1,973
Balance	668,816		668,816
Unrealized Gains on Available-for-Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance			(686)
Other comprehensive income			1
Balance	(685)		(685)
Accumulated other comprehensive loss
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance			(686)
Balance	$ (685)		$ (685)