Shareholders' Equity (Details) - USD ($) |
3 Months Ended | 9 Months Ended | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Sep. 30, 2018 |
Jun. 30, 2018 |
Mar. 31, 2018 |
Dec. 31, 2017 |
Sep. 30, 2017 |
Jun. 30, 2017 |
Mar. 31, 2017 |
Sep. 30, 2018 |
Sep. 30, 2017 |
Jul. 21, 2016 |
|
| Shareholders' Equity [Line Items] | ||||||||||
| Stock Repurchase Program, Number of Shares Authorized to be Repurchased | 3,000,000 | |||||||||
| Stock Repurchased and Retired During Period, Shares | 267,451 | 579,769 | 764,617 | 826,633 | ||||||
| Stock Repurchased and Retired During Period, In Total Dollars | $ 16,820,000 | $ 29,988,000 | $ 44,985,000 | $ 41,983,000 | ||||||
| Stock repurchased, common stock acquired, average cost per share | $ 62.89 | $ 51.72 | $ 58.83 | $ 50.79 | ||||||
| Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased | 1,054,048 | 1,054,048 | ||||||||
| Common Stock [Member] | ||||||||||
| Shareholders' Equity [Line Items] | ||||||||||
| Dividends per share (in dollars per share) | $ 0.15 | $ 0.15 | $ 0.15 | $ 0.15 | $ 0.15 | $ 0.15 | $ 0.15 | $ 0.45 | $ 0.45 | |
| X | ||||||||||
- Definition Shareholders' Equity [Line Items] No definition available.
|
| X | ||||||||||
- Definition Aggregate dividends declared during the period for each share of common stock outstanding. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition The cash outflow to reacquire common stock during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan. No definition available.
|
| X | ||||||||||
- Definition The remaining number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan. No definition available.
|
| X | ||||||||||
- Definition Number of shares that have been repurchased and retired during the period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Definition Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital). Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Details
|