Recent Accounting Standards Recent Accounting Standards (Details) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2017 |
Mar. 31, 2016 |
|
| New Accounting Pronouncements and Changes in Accounting Principles [Abstract] | ||
| Net periodic costs excluding service costs | $ 0.8 | $ 2.1 |
| Restricted cash | $ 4.6 | $ 2.0 |