Revenue (Tables)

3 Months Ended

Mar. 31, 2018

Revenue from Contract with Customer [Abstract]

Short and Long-Term Contract Assets, Liabilities, and Receivables

The Company’s accounts receivables and current and long-term contract assets and liabilities are summarized in the following table.

(Thousands of dollars)
	Accounts Receivable, Less Allowance		Contract Assets (Current)		Contract Assets (Long-Term)		Contract Liabilities (Current)		Contract Liabilities (Long-Term)
Balance at January 1, 2018	$	2,104,555	$	33,031	$	135,150	$	208,909	$	8,745
Balance at March 31, 2018	$	2,326,411	$	34,316	$	135,581	$	153,037	$	8,745