Discontinued Operations (Details) - USD ($) $ in Millions		3 Months Ended								12 Months Ended
	Jun. 30, 2021	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Gain on sale of discontinued operations										$ 216.9	$ 0.0	$ 0.0
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Income from discontinued operations, net of income taxes		$ 19.6	$ 145.7	$ 6.9	$ 5.9	$ 7.1	$ 5.6	$ 5.3	$ 4.7	178.1	22.7	25.0
Disposal Group, Including Discontinued Operation, Cash Flow Disclosures [Abstract]
Cash received from sale of discontinued operations											0.0	0.0
Oxford Business | Discontinued Operations, Held-for-sale
Disposal Group, Including Discontinued Operation, Assets [Abstract]
Accounts receivable, net						75.9					75.9
Prepaid expenses and income taxes						0.8					0.8
Other current assets						0.7					0.7
Property and equipment, net						14.5					14.5
Operating lease right-of-use assets						11.9					11.9
Identifiable intangible assets, net						18.0					18.0
Goodwill						197.7					197.7
Other non-current assets						2.4					2.4
Total assets of discontinued operations						321.9					321.9
Accounts payable						1.5					1.5
Accrued payroll and contract professional pay						27.5					27.5
Operating lease liabilities						5.1					5.1
Other current liabilities						5.6					5.6
Operating lease liabilities, long-term						7.5					7.5
Other long-term liabilities						4.0					4.0
Total liabilities of discontinued operations						$ 51.2					51.2
Oxford Business | Discontinued Operations
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Proceeds from Sale of Property Held-for-sale	$ 525.0
Disposal Group, Including Discontinued Operation, Income Statement Disclosures [Abstract]
Revenues										324.3	448.5	508.3
Costs of services										223.0	306.4	349.9
Gross profit										101.3	142.1	158.4
Selling, general and administrative expenses										90.1	112.3	125.2
Amortization of intangible assets										0.4	0.7	0.7
Income before income taxes										10.8	29.1	32.5
Provision for income taxes										1.5	6.4	7.5
Gain on sale, net of income taxes										168.8	0.0	0.0
Income from discontinued operations, net of income taxes										178.1	22.7	25.0
Disposal Group, Including Discontinued Operation, Cash Flow Disclosures [Abstract]
Net cash provided by (used in) operating activities										(84.0)	49.9	40.7
Cash received from sale of discontinued operations										503.8	0.0	0.0
Other										(3.9)	(6.4)	(6.3)
Net cash provided by (used in) investing activities										$ 499.9	$ (6.4)	$ (6.3)