Merger Agreement (Details) - USD ($)		3 Months Ended			9 Months Ended		12 Months Ended
	Dec. 14, 2021	Sep. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021	Dec. 31, 2021
Merger Agreement [Line Items]
Common stock, par value	$ 0.01	$ 0.01			$ 0.01		$ 0.01
Preferred stock, par value	$ 25
Cash dividend		$ 200,000,000.0	$ 265,000,000.0		$ 465,000,000.0	$ 138,400,000
Merger costs, net		$ 11,500,000		$ 36,500,000	36,800,000	776,600,000
Cash payments for merger costs					32,300,000	2,125,700,000
Reimbursement of merger termination fee					$ 0	2,100,000,000
Merger Costs, Net [Member] | Merger Termination Fee [Member]
Merger Agreement [Line Items]
Cash payments for merger costs							$ 1,400,000,000
Reimbursement of merger termination fee							$ 1,400,000,000
Canadian Pacific Railway Limited (CP)
Merger Agreement [Line Items]
Common shares received in exchange for each common share of the Company.	2.884
Cash received, in addition to shares, in exchange for each common share of the Company	$ 90
Cash received in exchange for each preferred share of the Company	37.50
Merger cash and stock transaction, value per common share	$ 301.20
Canadian National Railway Company (CN)
Merger Agreement [Line Items]
Termination fee that the Company was required to pay to terminate its merger agreement.						$ 700,000,000