Revenue Recognition (Contract Liabilities) (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Change In Contract With Customer, Asset And Liability [Roll Forward]
Contract Assets, Beginning balance	$ 0
Contract Liabilities, Current, Beginning balance	0
Revenue recognized that was included in contract liabilities at the beginning of the period	384	$ 0
Amounts transferred from contract assets to receivables	(48,907)	$ 0
Contract Assets, Ending balance	257,224
Contract Liabilities, Current, Ending balance	171,940
Short-term Contract with Customer
Change In Contract With Customer, Asset And Liability [Roll Forward]
Contract Assets, Beginning balance	219,361
Revenue recognized that was included in contract liabilities at the beginning of the period	0
Increase due to revenue recognized in the period in excess of billings	334,815
Increase due to billings arising during the period in excess of revenue recognized	0
Amounts transferred from contract assets to receivables	(279,360)
Other contract asset, net	(17,592)
Long-term Contract with Customer
Change In Contract With Customer, Asset And Liability [Roll Forward]
Contract Assets, Beginning balance	3,990
Revenue recognized that was included in contract liabilities at the beginning of the period	0
Increase due to revenue recognized in the period in excess of billings	405
Increase due to billings arising during the period in excess of revenue recognized	0
Amounts transferred from contract assets to receivables	(2,167)
Other contract asset, net	(435)
Contract Assets, Ending balance	1,793
Short-term Contract with Customer, Liability
Change In Contract With Customer, Asset And Liability [Roll Forward]
Contract Liabilities, Current, Beginning balance	178,515
Revenue recognized that was included in contract liabilities at the beginning of the period	(99,538)
Increase due to revenue recognized in the period in excess of billings	0
Increase due to billings arising during the period in excess of revenue recognized	107,080
Amounts transferred from contract assets to receivables	0
Other contract liability, net	(14,117)
Long-term Contract With Customer, Liability
Change In Contract With Customer, Asset And Liability [Roll Forward]
Contract Liabilities, Noncurrent, Beginning balance	3,925
Revenue recognized that was included in contract liabilities at the beginning of the period	(659)
Increase due to revenue recognized in the period in excess of billings	0
Increase due to billings arising during the period in excess of revenue recognized	0
Amounts transferred from contract assets to receivables	0
Other contract liability, net	(838)
Contract Liabilities, Noncurrent, Ending balance	$ 2,428