Summary Stockholders' Equity (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
	Jan. 01, 2017	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Beginning balance	$ 191,755			$ 191,755
Net income		$ 17,368	$ 10,251	27,665	$ 15,076
Ending balance		229,397		229,397
Common Stock
Beginning balance	50			50
Exercise of stock options				1
Ending balance	50	51		51
Additional Paid-in Capital
Beginning balance	276,127			276,127
Cumulative-effect adjustment	211
Share-based compensation				4,087
Issuance of ESPP shares				907
Exercise of stock options				1,256
Equity issued on note conversion				2,984
Ending balance	276,338	285,572		285,572
Accumulated Deficit
Beginning balance	(84,288)			(84,288)
Cumulative-effect adjustment	181
Net income				27,665
Ending balance	$ (84,107)	$ (56,442)		$ (56,442)