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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No definition available.

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Fair value of obligations measured on a recurring basis.

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Amount of gain (loss) recognized on the income statement for 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 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		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 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	$ 31,000,000		$ 31,000,000
Acquisition-related contingent consideration liabilities, range of potential undiscounted earn-out liabilities, high	217,000,000		217,000,000
Acquisition-related contingent consideration liabilities, net increase (decrease), measurement period adjustments			2,900,000
Earn-Out Liabilities [Member]
Fair Value, Financial Instruments Measured on a Recurring Basis [Line Items]
Acquisition-related contingent consideration liabilities, estimated fair value	140,700,000		140,700,000		$ 118,100,000
Acquisition-related contingent consideration liabilities, additions from new business combinations	1,000,000.0	$ 0	16,200,000	$ 1,500,000
Acquisition-related contingent consideration liabilities, net increase (decrease), fair value adjustments, expense (income)	29,200,000	4,400,000	36,500,000	4,400,000
Acquisition-related contingent consideration liabilities, net increase (decrease), measurement period adjustments		(700,000)		2,000,000.0
Acquisition-related contingent consideration liabilities, payments	30,000,000.0	$ 23,100,000	30,000,000	$ 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	$ 51,200,000		$ 51,200,000		$ 29,600,000