Equity Method Investments (Tables)

12 Months Ended

Dec. 31, 2020

Equity Method Investments and Joint Ventures [Abstract]

Equity Method Investments

The table below summarizes the book value of those investments and related financing receivables, which are reported in “Investments and other assets” in the consolidated balance sheets, and the related “Loss (income) from equity affiliates”:

	Book Value at				Loss (Income) from Equity Affiliates
	December 31,				Year Ended December 31,
	2020		2019		2020		2019		2018
	(Dollars in millions)
Equity method investment and financing receivables related to Middlemount	$	24.6	$	56.3	$	60.1	$	(9.0)	$	(69.3)
Other equity method investments	—		0.6		—		5.6		1.2
Total equity method investments and financing receivables related to Middlemount	$	24.6	$	56.9	$	60.1	$	(3.4)	$	(68.1)