Stock-Based Compensation (Summary Of The Status Of Nonvested Share Awards) (Details)	6 Months Ended
	Jun. 30, 2018 $ / shares shares
Nonvested Share Awards [Roll Forward]
Nonvested, Shares, Beginning Balance | shares	1,254,518
Granted, Shares | shares	225,764
Vested, Shares | shares	(344,830)
Forfeited, Shares | shares	(15,049)
Nonvested, Shares, Ending Balance | shares	1,120,403
Nonvested, Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 38.67
Granted , Weighted Average Grant Date Fair Value | $ / shares	59.23
Vested , Weighted Average Grant Date Fair Value | $ / shares	32.27
Forfeited , Weighted Average Grant Date Fair Value | $ / shares	45.88
Nonvested , Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 44.69