Subsequent events - Schedule of debt exchange (Details) - Subsequent Event - Senior Notes - USD ($) $ in Millions	Apr. 19, 2023	Apr. 24, 2023
Subsequent Event [Line Items]
Aggregate Principal Amount Tendered and Consents Received	$ 3,014
Percentage of Total Outstanding Principal Amount of such Series of Old Notes Tendered and Consenting	97.30%
Aggregate Principal Amount of CPRC Notes Issued	$ 3,014
0.03125
Subsequent Event [Line Items]
Interest rate	3.125%
Aggregate Principal Amount Tendered and Consents Received	$ 227
Percentage of Total Outstanding Principal Amount of such Series of Old Notes Tendered and Consenting	90.80%
Aggregate Principal Amount of CPRC Notes Issued	$ 227
0.02875
Subsequent Event [Line Items]
Interest rate	2.875%
Aggregate Principal Amount Tendered and Consents Received	$ 415
Percentage of Total Outstanding Principal Amount of such Series of Old Notes Tendered and Consenting	97.60%
Aggregate Principal Amount of CPRC Notes Issued	$ 415
0.043
Subsequent Event [Line Items]
Interest rate	4.30%
Aggregate Principal Amount Tendered and Consents Received	$ 448
Percentage of Total Outstanding Principal Amount of such Series of Old Notes Tendered and Consenting	100.00%
Aggregate Principal Amount of CPRC Notes Issued	$ 448
0.0495
Subsequent Event [Line Items]
Interest rate	4.95%
Aggregate Principal Amount Tendered and Consents Received	$ 463
Percentage of Total Outstanding Principal Amount of such Series of Old Notes Tendered and Consenting	92.80%
Aggregate Principal Amount of CPRC Notes Issued	$ 463
0.047
Subsequent Event [Line Items]
Interest rate	4.70%
Aggregate Principal Amount Tendered and Consents Received	$ 498
Percentage of Total Outstanding Principal Amount of such Series of Old Notes Tendered and Consenting	99.60%
Aggregate Principal Amount of CPRC Notes Issued	$ 498
0.035
Subsequent Event [Line Items]
Interest rate	3.50%
Aggregate Principal Amount Tendered and Consents Received	$ 543
Percentage of Total Outstanding Principal Amount of such Series of Old Notes Tendered and Consenting	98.70%
Aggregate Principal Amount of CPRC Notes Issued	$ 543
0.042
Subsequent Event [Line Items]
Interest rate	4.20%
Aggregate Principal Amount Tendered and Consents Received	$ 420
Percentage of Total Outstanding Principal Amount of such Series of Old Notes Tendered and Consenting	98.90%
Aggregate Principal Amount of CPRC Notes Issued	$ 420
KCS Notes Due In May 2023
Subsequent Event [Line Items]
Aggregate Principal Amount Tendered and Consents Received		$ 445
KCS Notes Due In November 2023
Subsequent Event [Line Items]
Aggregate Principal Amount Tendered and Consents Received		$ 203