Shares and Stockholders' Equity (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Deferred compensation plan mark to market adjustment	$ (1.0)		$ (1.0)	$ 7.0
Maximum [Member]
Deferred compensation plan mark to market adjustment		$ 1.0