Stock-Based Compensation Plans (Summary Of Restricted Stock Units Activity) (Details) - Restricted Stock Units (RSUs) [Member] - USD ($) $ / shares in Units, $ in Millions		12 Months Ended
		Dec. 31, 2016		Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Outstanding, as of December 31		859,419
Granted		500
Converted		(404,096)
Outstanding, as of December 31		455,823	[1]	859,419
Vested		220,360
Weighted Average Grant-Date Fair Value Per Share, Outstanding as of December 31		$ 69.73
Weighted Average Grant-Date Fair Value Per Share, Nonvested, Granted		181.04		$ 139.00	$ 130.16
Weighted Average Grant-Date Fair Value Per Share, Nonvested, Converted		16.73
Weighted Average Grant-Date Fair Value Per Share, Outstanding as of December 31		101.75		$ 69.73
Weighted Average Grant-Date Fair Value Per Share, Vested as of December 31		$ 95.12
Aggregate Intrinsic Value, Outstanding	[2]	$ 99.1
Aggregate Intrinsic Value, Vested	[2]	$ 47.9
Weighted Average Remaining Contractual Term, Outstanding		6 years 2 months
Weighted Average Remaining Contractual Term, Vested		4 years 3 months

[1] No RSUs outstanding at December 31, 2016 were convertible to shares of common stock.

[2] The intrinsic value of RSUs is measured by applying the closing stock price as of December 31, 2016 to the applicable number of units.