Stock Compensation - Employee Stock Purchase Plan (Details) - Employee stock purchase plan |
12 Months Ended |
|---|---|
|
Dec. 31, 2016
$ / shares
shares
| |
| Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] | |
| Options outstanding, Beginning balance (in shares) | shares | 372,566 |
| Granted (in shares) | shares | 1,273,036 |
| Exercised (in shares) | shares | (1,362,202) |
| Options outstanding, Ending balance (in shares) | shares | 283,400 |
| Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract] | |
| Weighted-average exercise price, Outstanding, Beginning of period (in dollars per share) | $ / shares | $ 46.19 |
| Weighted-average exercise price, Granted (in dollars per share) | $ / shares | 55.51 |
| Weighted-average exercise price, Exercised (in dollars per share) | $ / shares | 51.50 |
| Weighted-average exercise price, Outstanding, End of period (in dollars per share) | $ / shares | $ 62.55 |