Revenue Recognition - Contract with Customer, Asset and Liability (Details) - USD ($) $ in Thousands	Mar. 31, 2018	Jan. 01, 2018
Revenue from Contract with Customer [Abstract]
Customer receivables	$ 2,378,000	$ 2,504,000
Contract liabilities	572,000	623,000
Contract assets	188,000	255,000
Accounts receivable, gross	2,537	2,659
Allowance for doubtful accounts receivable	$ 159,000	$ 155,000