Statements of Consolidated Cash Flows - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Operating Activities:
Net income (loss)	$ (53.5)	$ (104.0)	$ 20.2
Adjustments to reconcile net income (loss) to cash flows from operating activities:
Depreciation and amortization	134.9	152.4	147.7
Lease amortization and accretion expense	160.9	168.0	0.0
Lease payments	(135.0)	(155.1)	0.0
Paid-in-kind interest	42.4	0.0	0.0
Debt-related amortization	17.5	6.7	2.7
Equity-based compensation and employee benefits expense	21.8	18.6	20.3
Non-union pension settlement charge	3.6	1.8	10.9
Gains on property disposals, net	(45.3)	(13.7)	(20.8)
Loss on extinguishment of debt	0.0	11.2	0.0
Impairment charges	0.0	8.2	0.0
Deferred income tax benefit, net	(14.9)	(3.0)	(1.1)
Other noncash items, net	0.9	(0.3)	2.2
Changes in assets and liabilities, net:
Accounts receivable	(40.4)	7.1	16.6
Accounts payable	(3.6)	(14.8)	6.1
Other operating assets	(23.9)	(1.5)	5.4
Other operating liabilities	57.1	(60.1)	14.6
Net cash provided by operating activities	122.5	21.5	224.8
Investing Activities:
Acquisition of property and equipment	(140.6)	(143.2)	(145.4)
Proceeds from disposal of property and equipment	56.1	25.9	36.4
Net cash used in investing activities	(84.5)	(117.3)	(109.0)
Financing Activities:
Issuance of long-term debt, net	374.8	570.0	0.0
Repayment of long-term debt	(31.4)	(579.0)	(31.9)
Debt issuance costs	(12.0)	(12.7)	0.0
Payments for tax withheld on equity-based compensation	(0.6)	(0.9)	(2.0)
Net cash provided by (used in) financing activities	330.8	(22.6)	(33.9)
Net Increase (Decrease) In Cash and Cash Equivalents and Restricted Amounts Held in Escrow	368.8	(118.4)	81.9
Cash and Cash Equivalents and Restricted Amounts Held in Escrow, Beginning of Year	109.2	227.6	145.7
Cash and Cash Equivalents and Restricted Amounts Held in Escrow, End of Year	478.0	109.2	227.6
Supplemental Cash Flow Information:
Interest paid	(67.6)	(106.8)	(101.2)
Letter of credit fees paid	(7.1)	(6.8)	(7.0)
Income tax paid	$ (1.2)	$ (3.7)	$ (5.5)