Share-Based Payments (Options and Stock Appreciation Rights Outstanding) (Details) - USD ($) $ / shares in Units, $ in Millions	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Shares Available For Grant
Shares Available For Grant, Beginning Balance (in shares)	291,000
Shares Available For Grant, Exercised (in shares)	0
Shares Available For Grant, Forfeited (in shares)	0
Shares Available For Grant, Expired (in shares)	0
Shares Available For Grant, Granted (in shares)	0
Shares Available For Grant, Ending Balance (in shares)	291,000
Shares/Awards
Opening Balance (in shares)	19,268
Exercised (in shares)	(250)
Forfeited (in shares)	0
Expired (in shares)	0
Granted (in shares)	0
Ending Balance (in shares)	19,018
Weighted-Average Exercise Price (usd per share)
Beginning Balance (in usd per share)	$ 240.47
Exercised (in usd per share)	255.13
Forfeited (in usd per share)	0.00
Expired (in usd per share)	0.00
Granted (in usd per share)	0.00
Ending Balance (in usd per share)	$ 240.28
Liability Awards
Cash received from exercise of options	$ 0.7	$ 0.3
Total fair value of shares vested	$ 0.2	0.0
SAR
Liability Awards
Opening balance (in shares)	77,178
Exercised (in shares)	(1,728)
Forfeited (in shares)	0
Granted (in shares)	11,715
Closing balance (in shares)	87,165.000
Total intrinsic value of options exercised	$ 0.2	0.1
Total share-based liabilities paid	$ 0.2	$ 0.1
RSU
Liability Awards
Opening balance (in shares)	6,029
Exercised (in shares)	(2,563)
Forfeited (in shares)	(72)
Granted (in shares)	4,385
Closing balance (in shares)	7,779.000
PSU
Liability Awards
Opening balance (in shares)	5,426
Exercised (in shares)	0
Forfeited (in shares)	0
Granted (in shares)	4,526
Closing balance (in shares)	9,952