Segment Information (Net Sales by Region or Origin and Long-Lived Assets by Region of Domicile) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales:	$ 240,913	$ 280,086	$ 266,036	$ 215,337	$ 258,112	$ 274,574	$ 247,627	$ 206,605	$ 1,002,372	$ 986,918	$ 1,007,981
Long-lived assets	97,046				101,779				97,046	101,779	112,226
North America
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales:									990,772	977,942	963,797
Long-lived assets	96,342				97,956				96,342	97,956	108,334
Europe
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales:									0	1,131	19,447
Long-lived assets	0				3,222				0	3,222	2,900
Asia
Revenues from External Customers and Long-Lived Assets [Line Items]
Net sales:									11,600	7,845	24,737
Long-lived assets	$ 704				$ 601				$ 704	$ 601	$ 992