Inventories (Tables)

3 Months Ended

Mar. 31, 2018

Inventory Disclosure [Abstract]

Summary of Inventories

	March 31, 2018		December 31, 2017
(Dollars in thousands)
Raw materials	$	56,094	$	59,353
Work in process		47,424		48,803
Finished goods		79,746		65,843
Inventories	$	183,264	$	173,999