Fair Value Measurements (Tables)

9 Months Ended

Sep. 30, 2015

Fair Value Disclosures [Abstract]

Fair value measurements

The estimated fair values for each type of instrument are presented below (in millions).

	September 30, 2015			Level One			Level Two			Level Three
Asset Class:
Mutual fund investments in a non-qualified retirement plan(a)	$	1.6		$	1.6		$	—		$	—
Total Assets	$	1.6		$	1.6		$	—		$	—
Liability Class:
Liabilities related to non-qualified retirement plan	$	(1.6	)	$	(1.6	)	$	—		$	—
Derivatives – natural gas instruments	(2.6		)	—			(2.6		)	—
Total Liabilities	$	(4.2	)	$	(1.6	)	$	(2.6	)	$	—

(a) Includes mutual fund investments of approximately 20% in the common stock of large-cap U.S. companies, approximately 5% in the common stock of small-cap U.S. companies, approximately 5% in international companies, approximately 5% in bond funds, approximately 35% in short-term investments and approximately 30% in blended funds.

	December 31, 2014			Level One			Level Two			Level Three
Asset Class:
Mutual fund investments in a non-qualified retirement plan(a)	$	1.9		$	1.9		$	—		$	—
Total Assets	$	1.9		$	1.9		$	—		$	—
Liability Class:
Liabilities related to non-qualified retirement plan	$	(1.9	)	$	(1.9	)	$	—		$	—
Derivatives – natural gas instruments	(3.4		)	—			(3.4		)	—
Total Liabilities	$	(5.3	)	$	(1.9	)	$	(3.4	)	$	—

(a) Includes mutual fund investments of approximately 15% in the common stock of large-cap U.S. companies, approximately 5% in the common stock of international companies, approximately 5% in bond funds, approximately 35% in short-term investments and approximately 40% in blended funds.