Annual report pursuant to Section 13 and 15(d)

Fair Value of Financial Instruments - Summary of Changes in Fair Value of Company's Earn-Out Liability (Details)

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Fair Value of Financial Instruments - Summary of Changes in Fair Value of Company's Earn-Out Liability (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Earn-out payments during period $ 3,627 $ 2,261 $ 518
Level 3 Inputs      
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Beginning balance 7,610 4,834  
Fair value of the earn-out liability associated with the MUSA-Galvanized / American Stainless acquisition 6,366 3,800  
Earn-out payments during period (4,075) (2,455)  
Changes in fair value during the period (747) 1,431  
Ending balance 9,154 7,610 4,834
MUSA-Stainless | Level 3 Inputs      
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Beginning balance 4,252 4,834  
Fair value of the earn-out liability associated with the MUSA-Galvanized / American Stainless acquisition 0 0  
Earn-out payments during period (1,634) (2,164)  
Changes in fair value during the period (215) 1,582  
Ending balance 2,403 4,252 4,834
MUSA-Galvanized | Level 3 Inputs      
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Beginning balance 3,358 0  
Fair value of the earn-out liability associated with the MUSA-Galvanized / American Stainless acquisition 0 3,800  
Earn-out payments during period (712) (291)  
Changes in fair value during the period (864) (151)  
Ending balance 1,782 3,358 0
American Stainless | Level 3 Inputs      
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]      
Beginning balance 0 0  
Fair value of the earn-out liability associated with the MUSA-Galvanized / American Stainless acquisition 6,366 0  
Earn-out payments during period (1,729) 0  
Changes in fair value during the period 332 0  
Ending balance $ 4,969 $ 0 $ 0