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Summary of Significant Accounting Policies - Summary of Effect of Adoption of ASU 2014-09 and Related ASUs (Detail) - USD ($) $ 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
Sales
Sales	$ 140,335	$ 185,112	$ 389,189	$ 540,064
Cost of Sales
Cost of Sales	81,887	98,621	241,012	295,238
Income before benefit for income taxes	3,220	19,207	(22,784)	45,421
(Provision) benefit for income taxes	4,369	(3,309)	11,889	(10,471)
Net income	7,589	15,898	(10,895)	34,950
Net Income (Loss)	7,589	15,898	(10,895)	34,950
ASSETS
Other receivables	30,084		30,084			$ 26,578
Inventory	106,060		106,060			122,542
Equity
Retained earnings	900,324		900,324			$ 922,178
Product [Member]
Sales
Sales	121,043	145,467	341,359	444,607
Cost of Sales
Cost of Sales	69,943	73,534	208,184	229,861
Service [Member]
Sales
Sales	19,292	39,645	47,830	95,457
Cost of Sales
Cost of Sales	11,944	$ 25,087	32,828	$ 65,377
ASU 2014-09 [member]
ASSETS
Other receivables					$ 26,952
Equity
Retained earnings					922,456
ASU 2014-09 [member] \| Balances Without Adoption of ASC 606 [Member]
Cost of Sales
Income before benefit for income taxes	2,492		(23,658)
(Provision) benefit for income taxes	3,382		10,938
Net income	5,874		(12,720)
Net Income (Loss)	5,874		(12,720)
ASSETS
Other receivables	27,917		27,917
Inventory	106,402		106,402
Equity
Retained earnings	898,499		898,499
ASU 2014-09 [member] \| Adjustments Due to ASU 2014-09 [Member]
Cost of Sales
Income before benefit for income taxes	728		874
(Provision) benefit for income taxes	987		951
Net income	1,715		1,825
Net Income (Loss)	1,715		1,825
ASSETS
Other receivables	2,167		2,167		374
Inventory	(342)		(342)
Equity
Retained earnings	1,825		1,825		$ 278
ASU 2014-09 [member] \| Product [Member] \| Balances Without Adoption of ASC 606 [Member]
Sales
Sales	120,588		341,464
Cost of Sales
Cost of Sales	69,754		208,480
ASU 2014-09 [member] \| Product [Member] \| Adjustments Due to ASU 2014-09 [Member]
Sales
Sales	455		(105)
Cost of Sales
Cost of Sales	189		(296)
ASU 2014-09 [member] \| Service [Member] \| Balances Without Adoption of ASC 606 [Member]
Sales
Sales	17,932		46,062
Cost of Sales
Cost of Sales	11,046		31,743
ASU 2014-09 [member] \| Service [Member] \| Adjustments Due to ASU 2014-09 [Member]
Sales
Sales	1,360		1,768
Cost of Sales
Cost of Sales	$ 898		$ 1,085