| Revolving credit facility expiring April 24, 2018 with interest payable monthly | Revolving credit facility expiring April 24, 2018 with interest payable monthly | Secured credit facility (secured by aircraft and related engines and components) due April 23, 2015 with floating interest rate, payable monthly | Secured credit facility (secured by aircraft and related engines and components) due April 23, 2015 with floating interest rate, payable monthly | Note payable due March 9, 2017 with floating interest rate, payable semi-annually on June 1 and December 1 | Note payable due March 9, 2017 with floating interest rate, payable semi-annually on June 1 and December 1 | Notes payable due January 15, 2022 with interest at 7.25% payable semi-annually on January 15 and July 15 | Notes payable due January 15, 2022 with interest at 7.25% payable semi-annually on January 15 and July 15 | Convertible notes payable | Convertible notes payable | Convertible notes payable | Convertible notes payable | Convertible notes payable | Convertible notes payable due March 1, 2014 with interest at 1.625% payable semi-annually on March 1 and September 1 | Convertible notes payable due March 1, 2014 with interest at 1.625% payable semi-annually on March 1 and September 1 | Convertible notes payable due March 1, 2014 with interest at 1.625% payable semi-annually on March 1 and September 1 | Convertible notes payable due March 1, 2014 with interest at 1.625% payable semi-annually on March 1 and September 1 | Convertible notes payable due February 1, 2015 with interest at 1.75% payable semi-annually on February 1 and August 1 | Convertible notes payable due February 1, 2015 with interest at 1.75% payable semi-annually on February 1 and August 1 | Convertible notes payable due March 1, 2016 with interest at 2.25% payable semi-annually on March 1 and September 1 | Convertible notes payable due March 1, 2016 with interest at 2.25% payable semi-annually on March 1 and September 1 | Convertible notes payable due March 1, 2016 with interest at 2.25% payable semi-annually on March 1 and September 1 | Convertible notes payable due February 1, 2026 with interest at 1.75% payable semi-annually on February 1 and August 1 | Convertible notes payable due February 1, 2026 with interest at 1.75% payable semi-annually on February 1 and August 1 | 7.25% bonds, 1.625% and 2.25% convertible notes | 7.25% bonds, 1.625% and 2.25% convertible notes | Remaining variable rate and fixed rate debt | Note payable due March 15, 2014 | Note payable due March 15, 2014 | Mortgage loan (secured by Wood Dale, Illinois facility) due August 1, 2015 with interest at 5.01% | Mortgage loan (secured by Wood Dale, Illinois facility) due August 1, 2015 with interest at 5.01% | Industrial revenue bond (secured by property, plant and equipment) due August 1, 2018 | Industrial revenue bond (secured by property, plant and equipment) due August 1, 2018 | Other | Other |