Revenue Recognition - Changes in Contract Assets and Contract Liabilities (Details) $ in Thousands	9 Months Ended
	Sep. 30, 2018 USD ($)
Accounts receivables current
Opening balance	$ 738,000
Closing balance	804,900
Contract with customer assets current
Contract Assets (Current)	67,000
Contract Assets (Current)	59,300
Contract with customer non-current asset
Contract Assets (Long-term)	46,900
Contract Assets (Long-term)	32,700
Contract with customer liability current
Contract Liabilities (Current)	218,370
Contract Liabilities (Current)	159,416
Contract with customer liability non-current
Contract Liabilities (Long-term)	135,000
Contract Liabilities (Long-term)	$ 65,000
2018	59.00%
Contract percentage recognized	47
2019	26
2020 or thereafter	15