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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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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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) (Narrative) (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Acquisition-related contingent consideration liabilities, range of potential undiscounted earn-out liabilities, low	$ 48,000,000		$ 48,000,000
Acquisition-related contingent consideration liabilities, range of potential undiscounted earn-out liabilities, high	225,000,000		225,000,000
Acquisition-related contingent consideration liabilities, net increase (decrease), measurement period adjustments			(200,000)
Earn-Out Liabilities [Member]
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Acquisition-related contingent consideration liabilities, estimated fair value	151,900,000		151,900,000		$ 118,100,000
Acquisition-related contingent consideration liabilities, additions from new business combinations	0	$ 0	16,200,000	$ 1,500,000
Acquisition-related contingent consideration liabilities, net increase (decrease), fair value adjustments, expense (income)	11,200,000	5,900,000	47,600,000	10,300,000
Acquisition-related contingent consideration liabilities, net increase (decrease), measurement period adjustments		2,200,000		4,200,000
Acquisition-related contingent consideration liabilities, payments	0	$ 0	30,000,000.0	$ 23,100,000
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	$ 57,500,000		$ 57,500,000		$ 29,600,000