Recent Accounting Guidance (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Jan. 01, 2018	Dec. 31, 2017
Revenue:
Revenue	$ 95,374		$ 336,892
Gross profit	39,913	$ 39,751	136,069	$ 113,527
Income from operations	10,668	13,835	48,437	37,078
Income before income taxes	9,346	12,855	44,458	33,693
Income tax provision	508	1,014	7,036	(1,586)
Net income	$ 8,838	$ 11,841	$ 37,422	$ 35,279
Net income per share:
Basic (in dollars per share)	$ 0.27	$ 0.38	$ 1.16	$ 1.15
Diluted (in dollars per share)	$ 0.26	$ 0.35	$ 1.10	$ 1.07
Consolidated Balance Sheet
Deferred income taxes	$ 76,382		$ 76,382			$ 83,148
Total assets	519,232		519,232			488,218
Deferred revenue	17,774		17,774			18,145
Total current liabilities	66,272		66,272			79,287
Total liabilities	122,158		122,158			134,608
Accumulated deficit	(165,723)		(165,723)			(204,745)
Total stockholders' equity	397,074		397,074			353,610
Total liabilities and stockholders' equity	519,232		519,232			$ 488,218
Product
Revenue:
Revenue	88,496		317,039
ASC 606 Adjustments
Revenue:
Revenue	556		(1,280)
Gross profit	556		(1,280)
Income from operations	556		(1,280)
Income before income taxes	556		(1,280)
Income tax provision	121		(277)
Net income	$ 435		$ (1,003)
Net income per share:
Basic (in dollars per share)	$ 0.01		$ (0.03)
Diluted (in dollars per share)	$ 0.01		$ (0.03)
Consolidated Balance Sheet
Deferred income taxes	$ 277		$ 277
Total assets	277		277
Deferred revenue	2,880		2,880
Total current liabilities	2,880		2,880
Total liabilities	2,880		2,880
Accumulated deficit	(2,603)		(2,603)
Total stockholders' equity	(2,603)		(2,603)
Total liabilities and stockholders' equity	277		277
ASC 606 Adjustments | Product
Revenue:
Revenue	556		(1,280)
ASC 606 Adjustments | ASU 2014-09
Consolidated Balance Sheet
Gross Reclassification Decrease In Contract With Customer Liability Due To New ASU Adoption	1,600		1,600		$ 1,600
Cumulative adjustment increase in retained earnings					$ 1,600
Before Topic 606
Revenue:
Revenue	95,930	$ 104,482	335,612	$ 294,165
Gross profit	40,469		134,789
Income from operations	11,224		47,157
Income before income taxes	9,902		43,178
Income tax provision	629		6,759
Net income	$ 9,273		$ 36,419
Net income per share:
Basic (in dollars per share)	$ 0.28		$ 1.13
Diluted (in dollars per share)	$ 0.27		$ 1.07
Consolidated Balance Sheet
Deferred income taxes	$ 76,659		$ 76,659
Total assets	519,509		519,509
Deferred revenue	20,654		20,654
Total current liabilities	69,152		69,152
Total liabilities	125,038		125,038
Accumulated deficit	(168,326)		(168,326)
Total stockholders' equity	394,471		394,471
Total liabilities and stockholders' equity	519,509		519,509
Before Topic 606 | Product
Revenue:
Revenue	$ 89,052		$ 315,759