Corporate Office Relocation (Narrative) (Details) - Home Office Relocation [Member] - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Restructuring Cost and Reserve [Line Items]
Employee severance, retention, relocation, and related costs	$ 8.3	$ 4.4	$ 16.3
Employee severance, retention, and relocation costs [Member]
Restructuring Cost and Reserve [Line Items]
Employee severance, retention, relocation, and related costs	1.0	2.0	7.6
Asset impairments [Member]
Restructuring Cost and Reserve [Line Items]
Employee severance, retention, relocation, and related costs	$ 7.3	$ 2.3	$ 8.7