Share-Based Compensation - Summary of SAR's Outstanding (Details) - $ / shares	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years
SARs
SARs, Shares Outstanding
Outstanding at beginning of year (in shares)	896,923	1,261,185	1,817,991
Granted (in shares)	69,742	70,141	88,042
Exercised (in shares)	(295,770)	(395,015)	(598,249)
Forfeited (in shares)	(31,193)	(39,388)	(46,161)
Expired (in shares)	(1,578)	0	(438)
Outstanding at end of year (in shares)	638,124	896,923	1,261,185
Exercisable at end of year (in shares)	417,856	489,357	595,086
Weighted- Average Exercise  Price
Outstanding at beginning of year (in USD per share)	$ 89.05	$ 75.71	$ 65.73
Granted (in USD per share)	253.62	205.12	149.75
Exercised (in USD per share)	67.96	66.82	55.93
Forfeited (in USD per share)	149.09	92.72	80.41
Expired (in USD per share)	166.52	0	108.20
Outstanding at end of year (in USD per share)	113.98	89.05	75.71
Exercisable at end of year (in USD per share)	$ 81.88	$ 70.37	$ 60.85
SARs | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period	4 years