Quarterly report pursuant to Section 13 or 15(d)

Significant Accounting Policies (Narrative) (Details)

v3.10.0.1
Significant Accounting Policies (Narrative) (Details) - USD ($)
$ in Thousands
3 Months Ended 9 Months Ended
Sep. 30, 2018
Sep. 30, 2018
Dec. 31, 2017
Accounting Policies [Abstract]      
Stock Repurchased and Retired During Period, Shares 194,001 521,342  
Stock Repurchase Program, Remaining Authorized Repurchase Amount $ 218,400 $ 218,400  
Stock Repurchased and Retired During Period, Value 29,200 76,600  
Debt and Capital Lease Obligations 45,000 45,000 $ 95,000
Stock Repurchase Program, Authorized Amount 250,000 250,000  
Long-term Debt, Fair Value $ 45,800 $ 45,800 $ 97,100