Revenue Recognition (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Contract with Customer, Asset, Gross	$ 629,435	$ 673,616
Contract with Customer, Liability, Current	15,995	$ 19,566
Contract with Customer, Liability, Revenue Recognized	8,000
Revenue, Remaining Performance Obligation, Amount	$ 28,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	2 years
Minimum [Member]
License Agreement, Term of Agreement	1 year
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	3.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	1 year
Maximum [Member]
License Agreement, Term of Agreement	7 years
Long-Duration Contracts, Assumptions by Product and Guarantee, Discount Rate	6.00%
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Period	3 years