Share-Based Compensation (Summary Of Changes In Nonvested Stock Units) (Details)	12 Months Ended
	Dec. 31, 2019 $ / shares shares
Restricted Stock Units (RSUs)
Shares [Roll Forward]
Nonvested at beginning of period (in shares) | shares	2,977,400
Granted (in shares) | shares	1,969,100
Vested (in shares) | shares	(347,100)
Cancelled/forfeited (in shares) | shares	(73,500)
Nonvested at period end (in shares) | shares	4,525,900
Weighted-Average Grant Date Fair Value [Roll Forward]
Granted, weighted-average grant date fair value, beginning of period (in dollars per share) | $ / shares	$ 30.10
Granted, weighted-average grant date fair value (in dollars per share) | $ / shares	21.24
Vested, weighted average grant date fair value (in dollars per share) | $ / shares	29.44
Cancelled/forfeited, weighted-average grant date fair value (in dollars per share) | $ / shares	27.79
Granted, weighted-average grant date fair value, period end ( in dollars per share) | $ / shares	$ 27.44
Performance Share Units
Shares [Roll Forward]
Nonvested at beginning of period (in shares) | shares	3,043,800
Granted (in shares) | shares	1,514,700
Vested (in shares) | shares	(597,600)
Cancelled/forfeited (in shares) | shares	(143,200)
Nonvested at period end (in shares) | shares	3,817,700
Weighted-Average Grant Date Fair Value [Roll Forward]
Granted, weighted-average grant date fair value, beginning of period (in dollars per share) | $ / shares	$ 27.02
Granted, weighted-average grant date fair value (in dollars per share) | $ / shares	24.99
Vested, weighted average grant date fair value (in dollars per share) | $ / shares	22.30
Cancelled/forfeited, weighted-average grant date fair value (in dollars per share) | $ / shares	27.94
Granted, weighted-average grant date fair value, period end ( in dollars per share) | $ / shares	$ 28.52