CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (DEFICIT) (Parenthetical)
Dec. 31, 2012
4 percent Convertible Senior Notes  
Stated interest rate 4.00%
Convertible debt | 4 percent Convertible Senior Notes  
Stated interest rate 4.00%
Convertible subordinated debt | 1 7/8 percent Convertible Senior Subordinated Notes  
Stated interest rate 1.875%