Acquisitions and Divestitures - Narrative (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2017 businesses_acquired businesses_divested	Sep. 30, 2016 businesses_acquired businesses_divested	Sep. 30, 2017 businesses_acquired businesses_divested	Sep. 30, 2016 businesses_acquired businesses_divested
Business Combinations [Abstract]
Divestiture activity | businesses_divested	0	0	0	0
Acquisition activity | businesses_acquired	1	0	2	0