| Year Ended December 31, | Six Months Ended June 30, | |||||||||||||||||||||||
| 2013 | 2014 | 2015 | 2016 | 2017 | 2018 | |||||||||||||||||||
| Fixed Charges: | ||||||||||||||||||||||||
| Interest expense | $ | 25,247 | $ | 29,074 | $ | 27,254 | $ | 50,298 | $ | 77,884 | $ | 52,204 | ||||||||||||
| Plus: estimated interest component of rent expense | 5,372 | 5,891 | 5,921 | 8,272 | 10,335 | 4,778 | ||||||||||||||||||
| Capitalized interest | 4,950 | 4,234 | 3,441 | 8,066 | 6,229 | 6,771 | ||||||||||||||||||
| Total Fixed Charges: | $ | 35,570 | $ | 39,199 | $ | 36,616 | $ | 66,636 | $ | 94,448 | $ | 63,753 | ||||||||||||
| Earnings: | ||||||||||||||||||||||||
| Income from continuing operations before income taxes | $ | 421,087 | $ | 507,855 | $ | 585,368 | $ | 412,837 | $ | 352,063 | $ | 207,355 | ||||||||||||
| Plus: Fixed charges | 35,570 | 39,199 | 36,616 | 66,636 | 94,448 | 63,753 | ||||||||||||||||||
| Less: capitalized interest | 4,950 | 4,234 | 3,441 | 8,066 | 6,229 | 6,771 | ||||||||||||||||||
| Total Earnings: | $ | 451,706 | $ | 542,820 | $ | 618,542 | $ | 471,407 | $ | 440,282 | $ | 264,337 | ||||||||||||
| Ratio of earnings to fixed charges | 12.70 | 13.85 | 16.89 | 7.07 | 4.66 | 4.15 | ||||||||||||||||||
