Goodwill and Other Intangible Assets, Goodwill (Details) $ in Millions	9 Months Ended	12 Months Ended
	Sep. 30, 2017 USD ($) segment	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Goodwill.
Goodwill, Beginning Balance	$ 3,678.8
Acquisition-related	192.7
Foreign currency translation	97.8
Goodwill, Ending Balance	$ 3,969.3	$ 3,678.8
Number of reportable business segments | segment	2
Goodwill impairment	$ 0.0	0.0	$ 0.0
Interconnect Products and Assemblies
Goodwill.
Goodwill, Beginning Balance	3,532.5
Acquisition-related	192.7
Foreign currency translation	97.8
Goodwill, Ending Balance	3,823.0	3,532.5
Cable Products and Solutions
Goodwill.
Goodwill, Beginning Balance	146.3
Goodwill, Ending Balance	$ 146.3	$ 146.3