Summary of Financial Statement Affected by Application of ASU 2014-09 and Related Amendments (Detail) - USD ($) $ / shares in Units, $ in Thousands		12 Months Ended
		Dec. 31, 2018		Dec. 31, 2017	Dec. 31, 2016
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Product revenues		$ 1,038,259		$ 985,683	$ 917,600
Type of Revenue [Extensible List]		us-gaap:ProductMember		us-gaap:ProductMember	us-gaap:ProductMember
Income tax expense		$ 16,220		$ 34,028	$ 33,965
Net Income		$ 41,899		$ 35,227	$ 76,598
Basic earnings per share		$ 1.17		$ 0.96	$ 2.10
Diluted earnings per share		$ 1.16		$ 0.96	$ 2.09
Balance Sheet December 31, 2018
Accounts receivable, net of allowance for doubtful accounts		$ 166,858		$ 185,058
Accrued liabilities		65,808	[1]	77,209
Unearned revenue		1,597	[1]	4,889
Deferred income taxes, net		62,847
Accumulated earnings		363,965		$ 293,645
Revenue Based on Previously Effective Guidance
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Product revenues		$ 1,035,773
Type of Revenue [Extensible List]		us-gaap:ProductMember
Income tax expense		$ 16,727
Net Income		$ 39,920
Basic earnings per share		$ 1.11
Diluted earnings per share		$ 1.10
Balance Sheet December 31, 2018
Accounts receivable, net of allowance for doubtful accounts		$ 166,858
Accrued liabilities	[1]	64,211
Deferred income taxes, net		62,522
Accumulated earnings		365,237
ASU 2014-09 | New Revenue Standard Adjustment
Revenue Initial Application Period Cumulative Effect Transition [Line Items]
Product revenues		$ 2,486
Type of Revenue [Extensible List]		us-gaap:ProductMember
Income tax expense		$ 507
Net Income		$ 1,979
Basic earnings per share		$ 0.06
Diluted earnings per share		$ 0.06
Balance Sheet December 31, 2018
Accrued liabilities	[1]	$ 1,597
Unearned revenue	[1]	1,597
Deferred income taxes, net		325
Accumulated earnings		$ (1,272)

[1] During 2018, unearned revenues associated with GPT and CSZ-IC were classified as liabilities held for sale. As of December 31, 2018, 5,351 in unearned revenues associated with GPT and CSZ-IC were classified as liabilities held for sale.