Share-based compensation plans - Stock activity - RSU, PSU, DSU (Details) - $ / shares	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Restricted Stock Units
Shares (in thousands)
Nonvested, beginning balance, shares	309,300
Granted, shares	147,000.0
Forfeited or expired, shares	(6,900)
Vested, shares	(113,800)
Nonvested, ending balance, shares	335,600	309,300
Weighted-Average Grant Date Fair Value Per Share
Nonvested, beginning balance (dollars per share)	$ 67.25
Granted (dollars per share)	66.29
Forfeited or expired (dollars per share)	63.98
Vested (dollars per share)	71.32
Nonvested, ending balance (dollars per share)	$ 65.52	$ 67.25
Performance Shares Units
Shares (in thousands)
Nonvested, beginning balance, shares	726,000.0
Granted, shares	213,900
Forfeited or expired, shares	(54,900)
Vested, shares	(171,500)
Nonvested, ending balance, shares	713,500	726,000.0
Weighted-Average Grant Date Fair Value Per Share
Nonvested, beginning balance (dollars per share)	$ 76.66
Granted (dollars per share)	69.14
Forfeited or expired (dollars per share)	86.94
Vested (dollars per share)	82.75
Nonvested, ending balance (dollars per share)	$ 72.15	$ 76.66
Expired, shares	(31,400)
Expired (dollars per share)	$ 94.52
Actual shares earned and distributed (shares)		208,100
Target shares (shares)		171,500
Deferred Stock Units
Shares (in thousands)
Nonvested, beginning balance, shares	19,700
Granted, shares	0
Vested, shares	0
Nonvested, ending balance, shares	19,700	19,700
Weighted-Average Grant Date Fair Value Per Share
Nonvested, beginning balance (dollars per share)	$ 54.74
Granted (dollars per share)	0
Vested (dollars per share)	0
Nonvested, ending balance (dollars per share)	$ 54.74	$ 54.74