Summary of Financial Statement Affected by Application of ASU 2014-09 and Related Amendments (Detail) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Product revenues	$ 258,939	$ 235,853	$ 784,607	$ 728,498
Type of Revenue [Extensible List]	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember	us-gaap:ProductMember
Income tax expense (benefit)	$ 3,688	$ 630	$ 9,807	$ 10,233
Net income (loss)	$ (355)	$ 6,554	$ 29,270	$ 40,469
Basic earnings (loss) per share	$ (0.01)	$ 0.18	$ 0.80	$ 1.10
Diluted earnings (loss) per share	$ (0.01)	$ 0.18	$ 0.80	$ 1.10
Balance Sheet September 30, 2018
Accounts receivable, net of allowance for doubtful accounts	$ 183,476		$ 183,476		$ 185,058
Accrued liabilities	72,544		72,544		77,209
Unearned revenue	6,128		6,128		4,889
Deferred income taxes, net	69,750		69,750
Accumulated earnings	351,336		351,336		$ 293,645
Revenue Based on Previously Effective Guidance
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Product revenues	$ 258,184		$ 782,451
Type of Revenue [Extensible List]	us-gaap:ProductMember		us-gaap:ProductMember
Income tax expense (benefit)	$ 3,842		$ 10,247
Net income (loss)	$ (956)		$ 27,554
Basic earnings (loss) per share	$ (0.03)		$ 0.76
Diluted earnings (loss) per share	$ (0.03)		$ 0.76
Balance Sheet September 30, 2018
Accounts receivable, net of allowance for doubtful accounts	$ 183,476		$ 183,476
Accrued liabilities	70,630		70,630
Unearned revenue	4,214		4,214
Deferred income taxes, net	69,360		69,360
Accumulated earnings	352,860		352,860
ASU 2014-09 | New Revenue Standard Adjustment
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Product revenues	$ 755		$ 2,156
Type of Revenue [Extensible List]	us-gaap:ProductMember		us-gaap:ProductMember
Income tax expense (benefit)	$ (154)		$ (440)
Net income (loss)	$ 601		$ 1,716
Basic earnings (loss) per share	$ 0.02		$ 0.04
Diluted earnings (loss) per share	$ 0.02		$ 0.04
Balance Sheet September 30, 2018
Accrued liabilities	$ 1,914		$ 1,914
Unearned revenue	1,914		1,914
Deferred income taxes, net	390		390
Accumulated earnings	$ (1,524)		$ (1,524)