Fair Value of Financial Instruments (Tables)

12 Months Ended

Dec. 31, 2017

Fair Value of Financial Instruments [Abstract]

Fair value of financial assets and liabilities on a recurring basis

The following table sets forth by level within the fair value hierarchy the Company's financial assets and liabilities accounted for at fair value on a recurring basis at the end of each of the past two years. Assets and liabilities are classified in their entirety based on the lowest level of input that is significant to the fair value measurement. The Company's assessment of the significance of a particular input to the fair value measurement requires judgment, and may affect the valuation of fair value assets and liabilities and their placement within the fair value hierarchy levels.

			Fair Value Measurements Using
Description	Asset / (Liability) Balance at 12/31/17		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(millions of dollars)
Deferred compensation plan assets	$	12.9	$	-	$	12.9	$	-
Supplementary pension plan assets		11.6		-		11.6		-
Interest rate swap		2.9		-		2.9		-

			Fair Value Measurements Using
Description	Asset / (Liability) Balance at 12/31/17		Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)
	(milliions of dollars)
Money market funds	$	0.7	$	0.7	$	-	$	-