Shareholders' Equity (Schedule Of Shares Reserved For Future Issuance) (Details)	Sep. 30, 2017 shares
Share-based Compensation Arrangement by Share-based Payment Award
Class A shares and Class B shares reserved for issuance	12,968,898
Conversion Of Class B To Class A Shares
Share-based Compensation Arrangement by Share-based Payment Award
Class A shares and Class B shares reserved for issuance	7,575,427
Employee Stock Purchase Plan
Share-based Compensation Arrangement by Share-based Payment Award
Class A shares and Class B shares reserved for issuance	2,000,000
2014 Long Term Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award
Class A shares and Class B shares reserved for issuance	1,992,436
2008 Stock Appreciation Rights Plan
Share-based Compensation Arrangement by Share-based Payment Award
Class A shares and Class B shares reserved for issuance	1,376,353
2003 Stock Option Plan
Share-based Compensation Arrangement by Share-based Payment Award
Class A shares and Class B shares reserved for issuance	24,682