Product Warranties (Tables)

9 Months Ended

Sep. 30, 2011

Product Warranties [Abstract]

Company's accrual for product warranty claims

(Thousands of dollars)	2011			2010
Balance at January 1	$	23,103		$	22,214
Charges to expense		23,177			14,315
Settlements		(19,507	)		(13,674	)
Balance at September 30	$	26,773		$	22,855