Repurchase of Common Stock (Details) - Stock Repurchase Plan - USD ($) |
6 Months Ended | 24 Months Ended | ||
---|---|---|---|---|
Aug. 17, 2016 |
Jun. 30, 2018 |
Dec. 31, 2017 |
Dec. 31, 2015 |
|
Class of Stock [Line Items] | ||||
Stock repurchase plan, amount approved | $ 50,000,000 | |||
Treasury stock repurchased (in shares) | 0 | 146,000 | ||
Treasury stock acquired, average price (in dollars per share) | $ 20.48 | |||
Treasury stock acquired, aggregate cost | $ 3,000,000 | |||
Stock repurchase plan, remaining amount approved | $ 25,100,000 | |||
Chairman and CEO | ||||
Class of Stock [Line Items] | ||||
Stock repurchase plan, amount approved (in shares) | 1,000,000 | |||
Stock repurchase plan, amount approved each month from CEO | $ 2,000,000 | |||
Average daily price of common stock for the preceding month discount, percent | 2.00% | |||
Treasury stock repurchased (in shares) | 1,000,000 | |||
Treasury stock acquired, average price (in dollars per share) | $ 21.92 | |||
Treasury stock acquired, aggregate cost | $ 21,900,000 |