Share-Based Compensation and Benefit Plans (Employee Share Purchase Plan Activity) (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Share-based Compensation [Abstract]
Stock Issued During Period, Shares, Employee Stock Purchase Plans	20,797	14,655	25,728
Weighted Average Fair Value Of Shares Purchased Under Employee Share Purchase Plan	$ 82.33	$ 74.66	$ 71.19
Employee Stock Ownership Plan (ESOP), Compensation Expense	$ 0.4	$ 0.2	$ 0.5