ARO Trust (Notes)

12 Months Ended

Dec. 31, 2017

Investments, Debt and Equity Securities [Abstract]

ARO TRUST

Available-for-Sale Investments

We are entitled to collect in rates the amounts necessary to fund our ARO. We deposit monthly, into an external trust account (ARO Trust), the revenues specifically designated for ARO. The ARO Trust carries a moderate risk portfolio. We measure the financial instruments held in our ARO Trust at fair value. However, in accordance with the ASC Topic 980, Regulated Operations, both realized and unrealized gains and losses of the ARO Trust are recorded as regulatory assets or liabilities.

Effective March 1, 2013, the annual funding obligation is approximately $36.4 million, with deposits made monthly.

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