General - Accounts Receivable, Contract Assets and Contract Liabilities (Details) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Dec. 31, 2017
General
Accounts receivable	$ 778,556	$ 679,269
Change in accounts receivable (in dollars)	$ 99,287
Change in accounts receivable (as a percent)	14.60%
Contract assets	$ 5,519	8,564
Change in contract assets (in dollars)	$ (3,045)
Change in contract assets (as a percent)	(35.60%)
Contract liabilities - current	$ 79,251	14,299
Change in contract liabilities - current (in dollars)	$ 64,952
Change in contract liabilities - current (as a percent)	454.20%
Contract liabilities - long-term	$ 13,192	$ 12,303
Change in contract liabilities - long-term (in dollars)	$ 889
Change in contract liabilities - long-term (as a percent)	7.20%
Revenue recognized previously included in current contract liabilities	$ 11,300
Estimated revenue to be recognized in 2018	78,500
Estimated revenue to be recognized in 2019	2,800
Estimated revenue to be recognized in 2020	2,600
Estimated revenue to be recognized in 2021 and beyond	$ 8,500

The aggregate of amounts due from customers or clients for goods or services that have been delivered or sold in the normal course of business and an amount representing an agreement for an unconditional promise by the maker to pay the entity (holder) a definite sum of money at a future date, reduced to their estimated net realizable fair value by an allowance established by the entity of the amount it deems uncertain of collection and net of any write-downs taken for collection uncertainty on the part of the holder, respectively.

No definition available.