Summary of Significant Accounting Policies - Business (Details)	12 Months Ended
	Dec. 31, 2018 item
Summary of Significant Accounting Policies
Minimum number of locations in which company operates metal service center network	300
Number of states in which the company operates metal service center network	40
Number of countries in which entity operates outside the U.S.	13
Minimum number of products the company distributes	100,000