Stock-Based Compensation (Summary Of The Status Of Nonvested Share Awards) (Details)	6 Months Ended
	Jun. 30, 2017 $ / shares shares
Nonvested Share Awards [Roll Forward]
Nonvested, Shares, Beginning Balance | shares	1,392,451
Granted, Shares | shares	233,520
Vested, Shares | shares	(394,130)
Forfeited, Shares | shares	(9,388)
Nonvested, Shares, Ending Balance | shares	1,222,453
Nonvested, Weighted Average Grant Date Fair Value, Beginning Balance | $ / shares	$ 34.67
Granted , Weighted Average Grant Date Fair Value | $ / shares	57.32
Vested , Weighted Average Grant Date Fair Value | $ / shares	30.79
Forfeited , Weighted Average Grant Date Fair Value | $ / shares	38.78
Nonvested , Weighted Average Grant Date Fair Value, Ending Balance | $ / shares	$ 40.22