Goodwill and Other Intangibles (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	May 31, 2016	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Business Acquisition [Line Items]
Business combination, goodwill acquired		$ 527.8		$ 527.8		$ 526.4
Acquired Finite-Lived Intangible Assets [Line Items]
Estimated future amortization expense for 2016		4.5		4.5
Estimated future amortization expense for 2017		9.0		9.0
Estimated future amortization expense for 2018		8.3		8.3
Estimated future amortization expense for 2019		8.2		8.2
Estimated future amortization expense for 2020		8.1		8.1
Other Intangible Assets
Acquired Finite-Lived Intangible Assets [Line Items]
Amortization expense related to other intangible assets		$ 2.2	$ 2.1	$ 4.3	$ 6.7
Aviate Global LLP
Business Acquisition [Line Items]
Business combination, consideration transferred, performance-related adjustment period	3 years
Business combination, consideration transferred	$ 18.8
Business combination, goodwill acquired	11.8
Business combination, intangible assets acquired	$ 4.5