Accounts Receivable - Transactions Affecting Allowance for Doubtful Accounts (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2016 |
Dec. 31, 2015 |
Dec. 31, 2014 |
|
| Receivables [Abstract] | |||
| Balance, beginning of year | $ 4.6 | $ 3.9 | $ 4.9 |
| Provisions charged to expense | 3.1 | 0.5 | 1.4 |
| Write-offs and other | (1.3) | 0.2 | (2.4) |
| Balance, end of year | $ 6.4 | $ 4.6 | $ 3.9 |