ARO Trust (Tables)

12 Months Ended

Dec. 31, 2018

Investments, Debt and Equity Securities [Abstract]

ARO Trust

Investments within the ARO Trust at fair value were as follows (in millions):

	December 31, 2018				December 31, 2017
	Amortized Cost Basis		Fair Value		Amortized Cost Basis		Fair Value
Money Market Funds	$	21.7	$	21.7	$	12.6	$	12.6
U.S. Equity Funds	46.4		56.8		35.9		50.5
International Equity Funds	21.9		21.4		20.7		24.6
Municipal Bond Funds	50.1		49.6		46.8		46.9
Total	$	140.1	$	149.5	$	116.0	$	134.6