Subsequent Events - Share Repurchases (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions |
1 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended |
---|---|---|---|---|
Nov. 08, 2018 |
Dec. 31, 2017 |
Sep. 30, 2018 |
Dec. 31, 2017 |
|
Subsequent Event [Line Items] | ||||
Shares repurchased during period (in shares) | (3.0) | (5.7) | ||
Value of shares repurchased during period | $ (8.0) | $ (23.8) | $ (52.8) | |
Weighted average price of shares repurchased (in dollars per share) | $ 7.86 | $ 9.22 | ||
Share repurchase program, unfulfilled requests (in shares) | 12.0 | |||
Share repurchase program, unfulfilled requests | $ 101.8 | |||
Estimated value per share (in dollars per share) | $ 8.50 | |||
Subsequent event | ||||
Subsequent Event [Line Items] | ||||
Shares repurchased during period (in shares) | (0.2) | |||
Value of shares repurchased during period | $ (2.1) | |||
Weighted average price of shares repurchased (in dollars per share) | $ 8.50 |