Restructuring Charges - Severance and Other Restructuring Costs Activity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018
Restructuring Reserve [Roll Forward]
Liability at beginning of period			$ 35,188
Charges	$ 31,213	$ 0	103,924	$ 0	$ 149,100
Payments/Utilization			(85,775)
Liability at end of period	53,337		53,337		53,337
Severance
Restructuring Reserve [Roll Forward]
Liability at beginning of period			29,794
Charges			61,735
Payments/Utilization			(48,611)
Liability at end of period	42,918		42,918		42,918
Other restructuring costs
Restructuring Reserve [Roll Forward]
Liability at beginning of period			5,394
Charges			42,189
Payments/Utilization			(37,164)
Liability at end of period	$ 10,419		$ 10,419		$ 10,419