Share-based Compensation	3 Months Ended
Share-based Compensation	Mar. 31, 2018
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share-based Compensation	Share-based Compensation On the Effective Date, pursuant to the operation of the Plan, the A.M. Castle & Co. 2017 Management Incentive Plan (the “MIP”) became effective. Pursuant to the Plan, on September 1, 2017, 1,734 shares, together with an aggregate original principal amount of $2,400 of Second Lien Notes (the "Restricted Notes") convertible into an additional 638 shares of new common stock as of the Effective Date, were issued as awards of restricted shares of the Company's common stock (the "Restricted Shares") under the MIP to certain officers of the Company. The Restricted Shares and Restricted Notes cliff vest on August 31, 2020, subject to the conditions set forth in the MIP. The Restricted Shares grant date fair value of $3.14 per share was based on the value of the common stock of the Successor company as calculated on the Effective Date pursuant to the Plan. As of March 31, 2018 (Successor), the unrecognized share-based compensation expense related to unvested Restricted Shares was $4,389 and the remaining unrecognized compensation cost is expected to be recognized over a weighted-average period of approximately 2.4 years. As discussed in Note 1 - Basis of Presentation, the Successor has elected to account for forfeitures as they occur. As of March 31, 2018 (Successor), the unrecognized share-based compensation expense related to the aggregate original principal amount of $2,400 of Second Lien Notes issued to certain officers of the Company was $1,853 and is expected to be recognized over a weighted-average period of approximately 2.4 years. The Company will recognize this expense on a straight-line basis over the three-year vesting period using the fair value at the issue date, $2,300.

The entire disclosure for compensation-related costs for equity-based compensation, which may include disclosure of policies, compensation plan details, allocation of equity compensation, incentive distributions, equity-based arrangements to obtain goods and services, deferred compensation arrangements, employee stock ownership plan details and employee stock purchase plan details.