Goodwill and Intangible Assets, Goodwill (Details) - USD ($)	3 Months Ended	12 Months Ended
	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill
Goodwill		$ 18,800,000	$ 37,200,000
Impairment of the carrying value of goodwill		18,400,000	0	$ 0
Goodwill impairment		18,400,000	0	0
Goodwill impairment		0
Fabricated Products
Goodwill
Goodwill		18,800,000	$ 37,200,000	$ 37,200,000
Goodwill impairment	$ (18,400,000)	$ (18,400,000)