Stock-Based Compensation - Unvested restricted stock and deferred shares activity (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Other Disclosures
Total unrecognized compensation cost related to the unvested awards	$ 17.9
Total weighted average remaining term of unvested awards	1 year 6 months 18 days
Compensation cost recognized	$ 21.2	$ 19.5	$ 20.2
Performance stock units
Summary of unvested restricted stock and deferred shares activity and related information
Unvested at beginning of year (in shares)	106	113	146
Granted (in shares)	67	79	99
Vested (in shares)	(68)	(80)	(125)
Cancelled/Forfeitures (in shares)	(6)	(6)	(7)
Unvested at end of year (in shares)	99	106	113
Weighted Average Grant Date Fair Value
Unvested at beginning of period (in dollars per share)	$ 170.42	$ 142.53	$ 107.29
Granted (in dollars per share)	179.19	162.23	106.37
Vested (in dollars per share)	143.93	122.88	73.62
Cancelled/Forfeitures (in dollars per share)	198.21	174.85	132.14
Unvested at end of period (in dollars per share)	$ 192.57	$ 170.42	$ 142.53
Other Disclosures
Total fair value of shares vested	$ 13.9	$ 16.6	$ 21.1
Total unrecognized compensation cost related to the unvested awards	$ 11.2
Total weighted average remaining term of unvested awards	1 year 6 months 4 days
Compensation cost recognized	$ 10.4	7.5	9.7
Aggregate intrinsic value of outstanding awards	$ 27.4
Performance stock units | Class A
Other Disclosures
Company's closing Common Stock price (in dollars per share)	$ 276.02
Second Amended And Restated 2004 Stock Incentive Plan | Restricted stock and deferred shares
Other Disclosures
Total fair value of shares vested	$ 10.6	$ 10.8	$ 12.7
Total unrecognized compensation cost related to the unvested awards	$ 5.3
Total weighted average remaining term of unvested awards	1 year 7 months 28 days
Compensation cost recognized	$ 9.6
Aggregate intrinsic value of outstanding awards	$ 23.6
Company's closing Common Stock price (in dollars per share)	$ 276.02
2004 Stock Incentive Plan | Restricted stock and deferred shares
Summary of unvested restricted stock and deferred shares activity and related information
Unvested at beginning of year (in shares)	86	93	121
Granted (in shares)	51	44	51
Vested (in shares)	(43)	(47)	(76)
Cancelled/Forfeitures (in shares)	(8)	(4)	(3)
Unvested at end of year (in shares)	86	86	93
Weighted Average Grant Date Fair Value
Unvested at beginning of period (in dollars per share)	$ 179.08	$ 149.96	$ 121.39
Granted (in dollars per share)	218.23	202.03	167.39
Vested (in dollars per share)	169.18	144.02	112.65
Cancelled/Forfeitures (in dollars per share)	209.15	169.9	139.46
Unvested at end of period (in dollars per share)	$ 204.24	$ 179.08	$ 149.96
Other Disclosures
Compensation cost recognized		$ 10.7	$ 9.3
Management Stock Purchase Plan | Restricted stock units (RSUs)
Summary of unvested restricted stock and deferred shares activity and related information
Granted (in shares)	18	20	26
Cancelled/Forfeitures (in shares)	(4)	(2)	(1)
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 67.63	$ 68.94	$ 57.5
Other Disclosures
Total unrecognized compensation cost related to the unvested awards	$ 1.4
Total weighted average remaining term of unvested awards	1 year 4 months 28 days
Compensation cost recognized	$ 1.2	$ 1.3	$ 1.2
Aggregate intrinsic value of outstanding awards	$ 7.4
Company's closing Common Stock price (in dollars per share)	$ 276.02
Dividend declared and unpaid	$ 0.1