Investments Long-Term Investments (Details) (USD $)
In Thousands, unless otherwise specified
 12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Fair Value Changes Recorded in Consolidated Statement of Operations [Abstract]      
Marketable Securities, Realized Gain $ 32,678 $ 29,441  
Available-for-sale Securities, Noncurrent 153,506 150,020  
Investments in Associated Companies [Abstract]      
Long-term investments 35,096 128,218  
Investments, All Other Investments [Abstract]      
Investments in and Advances to Affiliates, at Fair Value 11,263 42,653  
Long-term Investments 199,865 320,891  
Available-for-sale Securities, Fair Value changes Recorded in OCI [Abstract]      
Unrealized gains 3,118 9,275 41,026
Unrealized Losses Reclassified out of Accumulated Other Comprehensive Gain/Loss, Available for Sale Securities 828 0 177
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Net of Tax 2,290 9,275 40,849
Available-for-sale Securities, Fair Value Changes Recorded in Consolidated Statement of Operations [Abstract]      
Income (Loss) from investments held at fair value 18,967 (183) (411)
Equity Method Investments, Investments in Associated Companies [Abstract]      
Income (Loss) of associated companies, net of taxes 14,532 (13,593) 8,625
Income (Loss) of associated companies, net of taxes 14,204 (13,823) 10,305
Equity method investment, ownership percentage (as a percent) 54.30% 55.50%  
Other Investments at Fair Value - Related Party [Abstract]      
Loss from other investments - related party (8,329) (15,743) (3,220)
Cosine [Member]
      
Investments in Associated Companies [Abstract]      
Long-term investments 6,668 6,944  
Equity Method Investments, Investments in Associated Companies [Abstract]      
Income (Loss) of associated companies, net of taxes (328) (385) (440)
Equity method investment, ownership percentage (as a percent) 46.80% 46.80%  
Fox & Hound [Member]
      
Investments in Associated Companies [Abstract]      
Long-term investments 10,521 [1] 0 [1]  
Equity Method Investments, Investments in Associated Companies [Abstract]      
Income (Loss) of associated companies, net of taxes (403) 0 0
Equity method investment, ownership percentage (as a percent) 50.00% 0.00%  
SLI [Member]
      
Investments in Associated Companies [Abstract]      
Long-term investments 17,907 [2] 16,049 [2]  
Equity Method Investments, Investments in Associated Companies [Abstract]      
Income (Loss) of associated companies, net of taxes 1,796 (1,310) 7,779
Equity method investment, ownership percentage (as a percent) 24.10% 21.70%  
Steel Excel
      
Investments in Associated Companies [Abstract]      
Long-term investments 0 [3] 105,225 [3]  
Equity Method Investments, Investments in Associated Companies [Abstract]      
Income (Loss) of associated companies, net of taxes 13,139 (22,092) (10,439)
Equity method investment, ownership percentage (as a percent) 51.20% 40.30%  
API [Member]
      
Fair Value Changes Recorded in Consolidated Statement of Operations [Abstract]      
Marketable Securities, Realized Gain 32,678 [3] 15,818 [3]  
Available-for-sale Securities, Fair Value Changes Recorded in Consolidated Statement of Operations [Abstract]      
Other investments held at fair value 16,859 [3] 0 [3] 0 [3]
Equity Method Investments, Investments in Associated Companies [Abstract]      
Income (Loss) of associated companies, net of taxes 0 9,809 2,615
Equity method investment, ownership percentage (as a percent) 32.40% 32.40%  
Barbican
      
Fair Value Changes Recorded in Consolidated Statement of Operations [Abstract]      
Marketable Securities, Realized Gain 0 [1] 13,623 [1]  
Available-for-sale Securities, Fair Value Changes Recorded in Consolidated Statement of Operations [Abstract]      
Other investments held at fair value 2,108 [1] (183) [1] (411) [1]
DGT
      
Equity Method Investments, Investments in Associated Companies [Abstract]      
Income (Loss) of associated companies, net of taxes 0 213 886
Equity method investment, ownership percentage (as a percent) 59.20% 51.50%  
JPS [Member]
      
Equity Method Investments, Investments in Associated Companies [Abstract]      
Income (Loss) of associated companies, net of taxes 0 0 1,228
Equity method investment, ownership percentage (as a percent) 39.30% 39.30%  
Other [Member]
      
Equity Method Investments, Investments in Associated Companies [Abstract]      
Income (Loss) of associated companies, net of taxes 0 (58) 6
HNH
      
Equity Method Investments, Investments in Associated Companies [Abstract]      
Income (Loss) of associated companies, net of taxes 0 0 8,670
Available for Sale Securities, Noncurrent [Member]
      
Investments, All Other Investments [Abstract]      
Fair value 120,828 120,579  
Available-for-sale Securities, Fair Value changes Recorded in OCI [Abstract]      
Proceeds from sales 29,317 143,096 262,934
Gross realized gains 2,985 20,850 42,066
Gross losses from sales 0 (2,439) (3,668)
Available-for-sale Securities, Gross Realized Gain (Loss) 2,985 18,411 38,398
Change in net unrealized holding gains (losses) included in other comprehensive income 336 17,575 (37,188)
Computer Software and Services [Member] | Available for Sale Securities, Noncurrent [Member]
      
Investments, All Other Investments [Abstract]      
Fair value 3,824 [2],[3] 28,635 [2],[3]  
Aerospace/Defense [Member] | Available for Sale Securities, Noncurrent [Member]
      
Investments, All Other Investments [Abstract]      
Fair value 38,256 [2],[3] 21,630 [2],[3]  
Manufacturing [Member] | Available for Sale Securities, Noncurrent [Member]
      
Investments, All Other Investments [Abstract]      
Fair value 28,032 [2],[3] 31,455 [2],[3]  
Restaurants [Member] | Available for Sale Securities, Noncurrent [Member]
      
Investments, All Other Investments [Abstract]      
Fair value 15,012 [2],[3] 9,364 [2],[3]  
Other Industry [Member] | Available for Sale Securities, Noncurrent [Member]
      
Investments, All Other Investments [Abstract]      
Fair value 35,704 [2],[3] 29,495 [2],[3]  
SPII Liquidating Trust - Series B [Member]
      
Investments, All Other Investments [Abstract]      
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures 16 [1] 16,408 [1]  
SPII Liquidating Trust - Series D [Member]
      
Investments, All Other Investments [Abstract]      
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures 542 [1] 11,783 [1]  
SPII Liquidating Trust - Series G [Member]
      
Investments, All Other Investments [Abstract]      
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures 6,016 [1] 9,552 [1]  
SPII Liquidating Trust - Series H [Member]
      
Investments, All Other Investments [Abstract]      
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures 3,891 [1] 3,496 [1]  
SPII Liquidating Trust - Series I [Member]
      
Investments, All Other Investments [Abstract]      
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures 798 [1] 1,414 [1]  
Steel Partners II, L.P.
      
Equity Method Investments, Investments in Associated Companies [Abstract]      
Income (Loss) of associated companies, net of taxes (328) (230) 1,680
Other Investments at Fair Value - Related Party [Abstract]      
Loss from other investments - related party (8,329) (15,743) (3,220)
Proceeds from sales 23,061 4,156 13,494
Gross gains from sales 0 0 810
Equity Method Investment, Realized Loss on Disposal 0 0 0
Equity Method Investment, Realized Gain (Loss) on Disposal 0 0 810
Fair Value, Measurements, Recurring [Member] | Level 1
      
Investments, All Other Investments [Abstract]      
Fair value 79,352 87,907  
Fair Value, Measurements, Recurring [Member] | Level 2
      
Investments, All Other Investments [Abstract]      
Fair value $ 41,476 $ 32,672  
[1] Level 3 investment. For additional information related to the Company's Level 3 investments, see Note 6 - "Fair Value Measurements."
[2] Level 2 investment. Equity securities totaling $41,476 and $32,672 were classified as Level 2 investments as of December 31, 2012 and 2011, respectively.
[3] Level 1 investment. Equity securities totaling $79,352 and $87,907 were classified as Level 1 investments as of December 31, 2012 and 2011, respectively.