Condensed Consolidated Income Statements - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Income Statement [Abstract]
Net sales (Note 3)	$ 248,186	$ 194,255	$ 439,788	$ 370,365
Cost of sales	203,095	168,382	370,518	328,248
Startup and transition costs	10,540	3,055	16,699	6,361
Total cost of goods sold	213,635	171,437	387,217	334,609
Gross profit	34,551	22,818	52,571	35,756
General and administrative expenses	10,752	5,340	19,058	10,089
Income from operations	23,799	17,478	33,513	25,667
Other income (expense):
Interest income	11	28	30	49
Interest expense	(2,935)	(4,134)	(5,961)	(8,046)
Realized loss on foreign currency remeasurement	(1,233)	(18)	(2,614)	(457)
Miscellaneous income	258	154	578	344
Total other expense	(3,899)	(3,970)	(7,967)	(8,110)
Income before income taxes	19,900	13,508	25,546	17,557
Income tax provision	(6,042)	(1,953)	(8,143)	(4,256)
Net income	13,858	11,555	17,403	13,301
Net income attributable to preferred shareholders		2,438		4,875
Net income attributable to common shareholders	$ 13,858	$ 9,117	$ 17,403	$ 8,426
Weighted-average common shares outstanding:
Basic	33,737	4,238	33,737	4,238
Diluted	33,828	4,244	33,827	4,244
Net income per common share:
Basic	$ 0.41	$ 2.15	$ 0.52	$ 1.99
Diluted	$ 0.41	$ 2.15	$ 0.51	$ 1.99