Segment, Geographic and Product Line Information (Schedule of Net Sales by Product Line) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Energy carbon steel tubular products [Member]
Segment Reporting Information [Line Items]
Net sales	$ 1,695,545	$ 1,525,537	$ 1,873,620
Percentage of net sales	29.00%	29.00%	34.00%
Valves, fittings, flanges and all other products [Member]
Segment Reporting Information [Line Items]
Net sales	4,237,667	3,705,255	3,697,238
Percentage of net sales	71.00%	71.00%	66.00%
Line pipe [Member] | Energy carbon steel tubular products [Member]
Segment Reporting Information [Line Items]
Net sales	1,139,118	1,061,881	1,158,512
Percentage of net sales	19.00%	20.00%	21.00%
Oil country tubular goods (OCTG) [Member] | Energy carbon steel tubular products [Member]
Segment Reporting Information [Line Items]
Net sales	556,427	463,656	715,108
Percentage of net sales	10.00%	9.00%	13.00%
Valves and Specialty Products [Member] | Valves, fittings, flanges and all other products [Member]
Segment Reporting Information [Line Items]
Net sales	1,911,153	1,440,431	1,431,888
Percentage of net sales	32.00%	28.00%	26.00%
Carbon steel fittings and flanges and stainless steel and alloy pipe and fittings [Member] | Valves, fittings, flanges and all other products [Member]
Segment Reporting Information [Line Items]
Net sales	1,232,170	1,135,818	1,175,276
Percentage of net sales	21.00%	22.00%	21.00%
Other [Member] | Valves, fittings, flanges and all other products [Member]
Segment Reporting Information [Line Items]
Net sales	$ 1,094,344	$ 1,129,006	$ 1,090,074
Percentage of net sales	18.00%	21.00%	19.00%