Stock-Based Compensation (Summary Of Stock Option Activity) (Details) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, Outstanding at December 31, Number of Options	5,416,000
Stock options, Exercisable at December 31, Number of Options	3,428,000
Stock options, Outstanding at December 31, Weighted Average Exercise Price	$ 23.46
Unvested Stock Options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock options, Outstanding at January 1, Number of Options	5,623,000	3,622,000	3,313,000
Stock options, Granted, Number of Options	155,000	2,401,000	835,000
Stock options, Exercised, Number of Options	(45,000)	0	(402,000)
Stock options, Forfeited or expired, Number of Options	(317,000)	(400,000)	(124,000)
Stock options, Outstanding at December 31, Number of Options	5,416,000	5,623,000	3,622,000
Stock options, Outstanding at January 1, Weighted Average Exercise Price	$ 24.57	$ 35.41	$ 35.70
Stock options, Granted, Weighted Average Exercise Price	8.60	9.47	32.31
Stock options, Exercised, Weighted Average Exercise Price	7.74		30.60
Stock options, Forfeited or expired, Weighted Average Exercise Price	38.01	32.20	37.80
Stock options, Outstanding at December 31, Weighted Average Exercise Price	$ 23.46	$ 24.57	$ 35.41