Derivatives: Schedule of Derivatives (Tables)

6 Months Ended

Jun. 30, 2020

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Schedule of Derivative Instruments

Set forth below is information related to interest rate swap agreements:

(Millions, except for percentages)	June 30, 2020		December 31, 2019
De-designated portion, unamortized value:
Liabilities subject to compromise	$	6.1	$	6.1
Accumulated other comprehensive income	$	17.0	$	23.6

Schedule of Derivative Instruments, Gain (Loss) in Statement of Financial Performance

Changes in derivative instruments were as follows for the six-month period ended June 30:

(Millions)	2020			2019
Changes in fair value, net of tax	$	—		$	(2.4	)
Amortization of net unrealized gains on de-designated interest rate swaps,    net of tax	$	(4.9	)	$	(3.1	)