Annual report pursuant to Section 13 and 15(d)

Share-Based Compensation (Summary Of The Changes In The Number Of Outstanding Phantom Stock Shares) (Details) [Axis]

v3.8.0.1
Share-Based Compensation (Summary Of The Changes In The Number Of Outstanding Phantom Stock Shares) (Details) [Axis]
12 Months Ended
Dec. 31, 2017
shares
Employee Phantom Stock Plan [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Balance of shares outstanding at December 31, 2014 517,693
Granted 0
Settled (21,506)
Forfeited (4,722)
Balance of shares outstanding at December 31, 2015 491,465
Director Phantom Stock Plan [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Balance of shares outstanding at December 31, 2014 68,162
Granted 0
Settled 0
Forfeited 0
Balance of shares outstanding at December 31, 2015 68,162
Phantom Shares [Member]  
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]  
Balance of shares outstanding at December 31, 2014 585,855
Granted 0
Settled (21,506)
Forfeited (4,722)
Balance of shares outstanding at December 31, 2015 559,627