CONSOLIDATED BALANCE SHEETS (unaudited) (Parenthetical) - USD ($) $ in Thousands |
Sep. 30, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Statement Of Financial Position [Abstract] | ||
| Accounts receivable, allowance | $ 251,593 | $ 264,144 |
| Property and equipment, accumulated depreciation | 2,728,217 | 2,397,007 |
| Intangible assets, accumulated amortization | $ 895,034 | $ 770,691 |
| Preferred stock, par value | $ 0.001 | $ 0.001 |
| Preferred stock, shares authorized | 5,000,000 | 5,000,000 |
| Preferred stock, issued | 0 | 0 |
| Common stock, par value | $ 0.001 | $ 0.001 |
| Common stock, shares authorized | 450,000,000 | 450,000,000 |
| Common stock, shares issued | 217,338,629 | 217,120,346 |
| Common stock, shares outstanding | 200,778,434 | 209,754,247 |
| Treasury stock, shares | 16,560,195 | 7,366,099 |