Incentive Plans (Tables)

6 Months Ended

Jun. 30, 2021

Incentive Plans

Schedule of Valuation Assumptions

	Expected Stock Price		Risk-Free Interest
Award Date	Volatility		Rate
February 19, 2020	22	%	1.39	%
February 20, 2020	22	%	1.35	%
January 1, 2021	27	%	0.17	%
February 25, 2021	26	%	0.31	%

Schedule of Deferred Compensation

Below is a summary of our compensation expense and unearned compensation (in millions):

													Expected
													period to
	Deferred Compensation								Unearned Compensation				recognize
	Expensed				Capitalized				As of		As of		unearned
	Three Months Ended June 30,								June 30,		December 31,		compensation
Type of incentive award	2021		2020		2021		2020		2021		2020		(in years)
Long-term incentive units	$	2.8	$	3.1	$	—	$	—	$	24.9	$	15.1	2.3
Performance-based awards		6.4		6.6		0.1		0.2		47.2		34.4	2.8
Service-based restricted stock units		5.3		3.6		0.9		0.8		57.6		41.5	2.8
Interxion awards		4.1		7.1		—		—		12.8		27.2	1.9

	Six Months Ended June 30,
	2021		2020		2021		2020
Long-term incentive units	$	6.0	$	6.2	$	0.1	$	0.1
Performance-based awards		14.9		11.2		0.5		0.4
Service-based restricted stock units		9.2		6.8		1.6		1.6
Interxion awards		14.6		10.1		—		—

Summary of Long-Term Incentive Unit Activity

		Weighted-Average
		Grant Date Fair
Unvested Long-term Incentive Units	Units	Value
Unvested, beginning of period	235,535	$	122.22
Granted	132,041		138.05
Vested	(124,984)		122.22
Cancelled or expired	(1,876)		128.38
Unvested, end of period	240,716	$	130.86

Summary of Restricted Stock Activity

		Weighted-Average
		Grant Date Fair
Unvested Restricted Stock	Shares	Value
Unvested, beginning of period	783,219	$	123.04
Granted	243,107		135.44
Vested	(327,773)		120.04
Cancelled or expired	(30,366)		129.01
Unvested, end of period	668,187	$	128.75