Acquisition - Additional Information (Details)		3 Months Ended								12 Months Ended
	Oct. 01, 2018 USD ($) Employee t	Dec. 31, 2018 USD ($)	Sep. 30, 2018 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Business Acquisition [Line Items]
Goodwill		$ 153,463,000				$ 82,744,000				$ 153,463,000	$ 82,744,000
Intangible assets, net		93,614,000				58,859,000				93,614,000	58,859,000
Net sales		229,480,000	$ 209,855,000	$ 215,742,000	$ 211,209,000	$ 209,327,000	$ 210,120,000	$ 195,974,000	$ 184,941,000	866,286,000	800,362,000	$ 761,216,000
Operating income										21,942,000	33,252,000	(21,520,000)
Selling, general and administrative expenses										111,721,000	$ 110,534,000	$ 153,153,000
G P Business [Member]
Business Acquisition [Line Items]
Business acquisition purchase price	$ 186,000,000
Business acquisition, date of completion	Oct. 01, 2018
Annual production capacity | t	32,000
Number of employees at manufacturing facility | Employee	220
Goodwill		75,317,000								75,317,000
Intangible assets, net		43,600,000								43,600,000
Goodwill deductible for tax purposes		$ 0								$ 0
Acquired intangible assets estimated remaining life										13 years
Net sales										$ 23,100,000
Operating income										2,400,000
Selling, general and administrative expenses										$ 5,100,000
G P Business [Member] | Minimum [Member]
Business Acquisition [Line Items]
Acquired property, plant and equipment, estimated remaining lives										5 years
G P Business [Member] | Maximum [Member]
Business Acquisition [Line Items]
Acquired property, plant and equipment, estimated remaining lives										25 years