Summary of Significant Accounting Policies - Schedule of Changes in Restructuring Reserve (Parenthetical) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	$ 46.1	$ 7.3
Severance costs	15.2	74.2
Office closure costs		27.3
Other costs		9.2
Costs paid or utilized	38.0	71.9
Balance at end of year	23.3	46.1
Americas | United States
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	1.4	0.3
Severance costs		3.8
Office closure costs		17.8
Other costs		4.2
Costs paid or utilized	1.2	24.7
Balance at end of year	0.2	1.4
Southern Europe | France
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	0.6	0.0
Office closure costs	2.6	2.6
Other costs	1.2	1.2
Costs paid or utilized	3.2	3.2
Balance at end of year	0.6	0.6
Southern Europe | Italy
Restructuring Cost and Reserve [Line Items]
Balance, beginning of period	1.4	0.3
Severance costs		1.9
Office closure costs		0.5
Costs paid or utilized	1.1	2.3
Balance at end of year	$ 0.3	$ 1.4