Revenue Recognition and Accounts Receivable - Schedule of Net Increase to Opening Retained Earnings Due to Cumulative Impact of Adopting (Detail) - USD ($) $ in Thousands	Sep. 30, 2018	Jan. 01, 2018	Dec. 31, 2017	Sep. 30, 2017
Current assets
Cash and cash equivalents	$ 53,783		$ 81,157	$ 53,925
Accounts receivable, net	74,356		63,437
Inventories	79,895		81,330
Prepaid expenses and other current assets	34,517		25,877
Total current assets	245,010		251,801
Deferred income taxes	36,030		23,315
Other long-term assets	3,166		21,073
Total assets	450,165		405,354
Total liabilities	126,815		108,746
Shareholders’ equity
Common shares	1,854		1,828
Additional paid-in capital	238,422		220,591
Retained earnings	78,207		70,402
Accumulated other comprehensive income	4,867		3,787
Total shareholders’ equity	323,350		296,608
Total liabilities and shareholders’ equity	$ 450,165		405,354
Effect before Topic 606 [Member]
Current assets
Cash and cash equivalents			81,157
Accounts receivable, net			63,437
Inventories			81,330
Prepaid expenses and other current assets			25,877
Total current assets			251,801
Deferred income taxes			23,315
Other long-term assets			130,238
Total assets			405,354
Total liabilities			108,746
Shareholders’ equity
Common shares			1,828
Additional paid-in capital			220,591
Retained earnings			70,402
Accumulated other comprehensive income			3,787
Total shareholders’ equity			296,608
Total liabilities and shareholders’ equity			405,354
Impact of Adoption of Topic 606
Current assets
Accounts receivable, net			8,648
Inventories			(2,338)
Total current assets			6,310
Deferred income taxes			(1,549)
Total assets			4,761
Shareholders’ equity
Retained earnings			4,761
Total shareholders’ equity			4,761
Total liabilities and shareholders’ equity			$ 4,761
Topic 606 [Member]
Current assets
Cash and cash equivalents		$ 81,157
Accounts receivable, net		72,085
Inventories		78,992
Prepaid expenses and other current assets		25,877
Total current assets		258,111
Deferred income taxes		21,766
Other long-term assets		130,238
Total assets		410,115
Total liabilities		108,746
Shareholders’ equity
Common shares		1,828
Additional paid-in capital		220,591
Retained earnings		75,163
Accumulated other comprehensive income		3,787
Total shareholders’ equity		301,369
Total liabilities and shareholders’ equity		$ 410,115