Restructuring Charges - Severance and Other Restructuring Costs Activity (Details) - USD ($) $ in Thousands	3 Months Ended		18 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Mar. 31, 2019
Restructuring Reserve [Roll Forward]
Liability at beginning of period	$ 41,392
Charges	8,731	$ 24,900	$ 163,700
Payments/Utilization	(20,362)
Liability at end of period	29,761		29,761
Severance
Restructuring Reserve [Roll Forward]
Liability at beginning of period	27,670
Charges	2,958
Payments/Utilization	(12,673)
Liability at end of period	17,955		17,955
Other restructuring costs
Restructuring Reserve [Roll Forward]
Liability at beginning of period	13,722
Charges	5,773
Payments/Utilization	(7,689)
Liability at end of period	$ 11,806		$ 11,806