Shareholders' Equity (Details) - USD ($) |
3 Months Ended | 9 Months Ended | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
Sep. 30, 2015 |
Jun. 30, 2015 |
Mar. 31, 2015 |
Dec. 31, 2014 |
Sep. 30, 2014 |
Jun. 30, 2014 |
Mar. 31, 2014 |
Sep. 30, 2015 |
Sep. 30, 2014 |
Feb. 07, 2014 |
|
| Shareholders' Equity [Line Items] | ||||||||||
| Dividends per share (in dollars per share) | $ 0.12 | $ 0.12 | $ 0.36 | $ 0.36 | ||||||
| Stock Repurchase Program, Number of Shares Authorized to be Repurchased | 2,000,000 | |||||||||
| Stock Repurchase Program Number Of Shares Repurchased | 204,590 | 434,993 | 204,590 | 881,979 | ||||||
| Stock Repurchased and Retired During Period, In Total Dollars | $ 9,996,000 | $ 19,987,000 | $ 9,996,000 | $ 39,972,000 | ||||||
| Stock repurchased, common stock acquired, average cost per share | $ 48.86 | $ 45.95 | $ 48.86 | $ 45.32 | ||||||
| Stock Repurchase Program, Remaining Number of Shares Authorized to be Repurchased | 913,431 | 913,431 | ||||||||
| Common Stock [Member] | ||||||||||
| Shareholders' Equity [Line Items] | ||||||||||
| Dividends per share (in dollars per share) | $ 0.12 | $ 0.12 | $ 0.12 | $ 0.12 | $ 0.12 | $ 0.12 | $ 0.12 | |||