For contingent consideration arrangements recognized in connection with a business combination, this element represents an estimate of the high-end of the potential range (undiscounted) of the consideration which may be paid.

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For contingent consideration arrangements and indemnification assets recognized in connection with a business combination, this element represents an estimate of the low-end of the potential range (undiscounted) of the consideration which may be paid.

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Value of input used to measure contingent consideration liability from business combination.

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Fair value of obligations measured on a recurring basis.

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Amount of gain (loss) recognized in income from liability measured at fair value on recurring basis using unobservable input (level 3).

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Amount of purchases of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlements of financial instrument classified as a liability measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of increase (decrease) from adjustments after acquisition date under purchase accounting of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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Fair Value of Financial Instruments (Acquisition-Related Contingent Consideration and Other Liabilities) (Narrative) (Details)	3 Months Ended		9 Months Ended
	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Acquisition-related contingent consideration liabilities, range of potential undiscounted earn-out liabilities, low	$ 34,000,000		$ 34,000,000
Acquisition-related contingent consideration liabilities, range of potential undiscounted earn-out liabilities, high	$ 199,000,000		199,000,000
Acquisition-related contingent consideration liabilities, net increase (decrease), measurement period adjustments			$ 5,400,000
Discount Rate [Member] \| Minimum [Member]
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Acquisition-related contingent consideration liabilities, measurement input, discount rate	0.120		0.120
Discount Rate [Member] \| Maximum [Member]
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Acquisition-related contingent consideration liabilities, measurement input, discount rate	0.230		0.230
Discount Rate [Member] \| Weighted Average [Member]
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Acquisition-related contingent consideration liabilities, measurement input, discount rate	0.140		0.140
Earn-Out Liabilities [Member]
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Acquisition-related contingent consideration liabilities, estimated fair value	$ 132,800,000		$ 132,800,000		$ 173,200,000
Acquisition-related contingent consideration liabilities, additions from new business combinations	0	$ 0	7,200,000	$ 16,200,000
Acquisition-related contingent consideration liabilities, net increase (decrease), measurement period adjustments	0	0	1,100,000	0
Acquisition-related contingent consideration liabilities, net increase (decrease), fair value adjustments, expense (income)	0	11,200,000	1,700,000	47,600,000
Acquisition-related contingent consideration liabilities, payments	0	$ 0	50,400,000	$ 30,000,000.0
Earn-Out Liabilities [Member] \| Other Current Liabilities [Member]
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Acquisition-related contingent consideration liabilities, estimated fair value	$ 47,600,000		$ 47,600,000		$ 54,100,000