Significant Accounting Policies - Accounts Receivable (Details) - USD ($) $ in Thousands |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Organization, Consolidation and Presentation of Financial Statements [Abstract] | |||
| Third-Party Medicaid settlements receivable | $ 454 | ||
| Third-Party Medicaid settlements liability | 179 | $ 5,222 | |
| Allowance for Doubtful Accounts Receivable [Roll Forward] | |||
| Allowance for doubtful accounts, beginning balance | 18,322 | 5,329 | $ 5,028 |
| Provision for doubtful accounts | 24,212 | 23,578 | 9,509 |
| Accounts written off, net of recoveries | (12,662) | (10,585) | (9,208) |
| Allowance for doubtful accounts, ending balance | 29,872 | 18,322 | $ 5,329 |
| Optical products receivable | $ 7,042 | $ 8,434 | |