Acquisitions - Narrative (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended							0 Months Ended	12 Months Ended		12 Months Ended
	Dec. 31, 2012 Service_Center	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012 Service_Center	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2012 Trade name	Dec. 31, 2012 Customer relationships	Dec. 31, 2012 Non-compete agreements	Dec. 31, 2012 Developed technology	Dec. 31, 2011 Tube Supply	Dec. 31, 2012 Tube Supply Service_Center	Dec. 15, 2011 Tube Supply	Dec. 31, 2012 Tube Supply Trade name	Dec. 31, 2012 Tube Supply Customer relationships	Dec. 31, 2012 Tube Supply Non-compete agreements	Dec. 31, 2012 Tube Supply Developed technology	Dec. 31, 2011 Expense Related to Distribution or Servicing and Underwriting Fees
Business Acquisition [Line Items]
Business Acquisition, Percentage of Outstanding Common Shares Acquired																		100.00%
Service centers	49								49								2
Total purchase price	$ 184,385								$ 184,385
Business Acquisition, Cost of Acquired Entity, Transaction Costs					4,260					4,260						4,260
Acquired Intangible Assets, Weighted Average Useful Life									10 years 9 months 18 days			9 years 4 months 24 days	11 years 3 months 18 days	3 years	3 years		11 years 5 months
Intangible assets useful lives														3 years	3 years				10 years	12 years	3 years	3 years
Off-market lease unfavorable noncurrent	2,168				2,871				2,168	2,871
Off-market Lease, Current	645				645				645	645
Business combination, sales of acquiree since acquisition date, actual																7,648
Business combination, earnings or loss of acquiree since acquisition date, actual																901
Loss on extinguishment of debt									0	(6,153)	0
Net Sales	274,021	304,039	329,392	362,916	282,150	294,860	282,568	272,788	1,270,368	1,132,366	943,706
Interest Expense																							$ 7,366