Product Warranties (Tables)

3 Months Ended

Mar. 31, 2018

Product Warranties Disclosures [Abstract]

Changes in the Company's Accrual for Product Warranty Claims

Changes in the Company’s accrual for product warranty claims during the first three months of 2018 and 2017, including customer satisfaction settlements, were as follows:

(Thousands of dollars)
	2018			2017
Balance at January 1	$	151,425		$	34,419
Charges to expense	6,437			6,076
Settlements	(4,488		)	(7,508		)
Balance at March 31	$	153,374		$	32,987