Revenue - Contract Balances (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Contract with Customer, Asset, Net, Current [Roll Forward]
Contract with Customer, Receivable, Net, Current	$ 309,075	$ 184,993
Contract with Customer, Receivable, Current, Net Increase (Decrease)	(3,403)	47,263
Contract with Customer, Receivable, Net, Current	305,672	232,256
Contract with Customer, Asset, Gross, Current	2,833	0
Contract with Customer, Contract Asset, Current, Net Increase (Decrease)	(1,799)	46,960
Contract with Customer, Asset, Gross, Current	1,034	46,960
Contract with Customer, Asset, Net, Noncurrent [Roll Forward]
Contract with Customer, Receivable, Net, Noncurrent	60,948	34,008
Contract with Customer, Receivable, NonCurrent, Net Increase (Decrease)	3,628	19,728
Contract with Customer, Receivable, Net, Noncurrent	64,576	53,736
Contract with Customer, Asset, Gross, Noncurrent	541	0
Increase (Decrease) in Contract Receivables, Net	1,787	3,869
Contract with Customer, Asset, Gross, Noncurrent	2,328	3,869
Contract with Customer, Liability, Current [Roll Forward]
Contract with Customer, Liability, Current	4,016	3,147
Contract with Customer, Liability, Current, Net Increase (Decrease)	912	7,011
Contract with Customer, Liability, Current	4,928	10,158
Contract with Customer, Liability, Noncurrent [Roll Forward]
Contract with Customer, Liability, Noncurrent	1,731	1,834
Contract with Customer, Liability, Noncurrent, Net Increase (Decrease)	(1,116)	(103)
Contract with Customer, Liability, Noncurrent	$ 615	$ 1,731