Share-Based Compensation Plans (Options) (Details) - Employee Stock Option [Member] - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Number of Shares
Options outstanding, beginning balance (in shares)	1,504
Options exercised (in shares)	(318)
Options outstanding, ending balance (in shares)	1,186
Options exercisable (in shares)	1,186
Weighted Average Exercise Price
Options outstanding, beginning balance (usd per share)	$ 20.67	$ 21.22
Options exercised (usd per share)	23.25
Options outstanding, ending balance (usd per share)	20.67	$ 21.22
Options exercisable (usd per share)	$ 20.67
Weighted Average Remaining Contractual Term
Options exercisable, Weighted Average Remaining Contractual Term	2 years 3 months 11 days
Aggregate Intrinsic Value
Options exercisable, Aggregate Intrinsic Value	$ 30,295