Goodwill and Intangible Assets Goodwill (Details) - USD ($)	3 Months Ended			6 Months Ended	9 Months Ended
	Sep. 30, 2017	Jun. 30, 2017	Sep. 30, 2016	Jun. 30, 2017	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Goodwill [Line Items]
Goodwill, Acquired During Period		$ 3,300,000
Goodwill	$ 452,700,000		$ 449,400,000		$ 452,700,000	$ 449,400,000	$ 449,400,000
Goodwill, Impaired, Accumulated Impairment Loss	0				0
Amortization of intangible assets	$ 17,200,000		$ 15,500,000		$ 48,200,000	$ 46,600,000
Weighted Average [Member]
Goodwill [Line Items]
Finite-Lived Intangible Assets, Remaining Amortization Period					5 years 2 months 12 days
Trade name [Member]
Goodwill [Line Items]
Finite-Lived Intangible Asset, Useful Life	2 years			10 years