ARO Trust (Tables)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

Investments in available-for-sale securities within the ARO Trust at fair value were as follows (in millions):



	December 31, 2017				December 31, 2016
	Amortized Cost Basis		Fair Value		Amortized Cost Basis		Fair Value
Cash and Money Market Funds	$	12.6	$	12.6	$	5.0	$	5.0
U.S. Equity Funds	35.9		50.5		29.4		36.5
International Equity Funds	20.7		24.6		19.2		18.6
Municipal Bond Funds	46.8		46.9		36.7		36.3
Total	$	116.0	$	134.6	$	90.3	$	96.4

- Definition

Tabular disclosure of available-for-sale securities which includes, but is not limited to, changes in the cost basis and fair value, fair value and gross unrealized gain (loss), fair values by type of security, contractual maturity and classification, amortized cost basis, contracts to acquire securities to be accounted for as available-for-sale, debt maturities, transfers to trading, change in net unrealized holding gain (loss) net of tax, continuous unrealized loss position fair value, aggregate losses qualitative disclosures, other than temporary impairment (OTTI) losses or other disclosures related to available for sale securities.

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