Fair Value Measurements (Fair Values of Financial Instruments Measured On Recurring Basis) (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Debt	$ 2,000,000	$ 2,000,000
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value	10,391	11,076
Contingent consideration	9,296	9,094
Debt	1,975,779	1,960,527
Total liabilities measured at fair value	1,985,075	1,969,621
Fair Value \| Money market and other funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market and other funds	10,391	10,413
Fair Value \| Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Corporate debt securities	0	663
Fair Value \| Level 1
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value	10,391	10,413
Contingent consideration	0	0
Debt	1,975,779	1,960,527
Total liabilities measured at fair value	1,975,779	1,960,527
Fair Value \| Level 1 \| Money market and other funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market and other funds	10,391	10,413
Fair Value \| Level 1 \| Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Corporate debt securities	0	0
Fair Value \| Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value	0	663
Contingent consideration	0	0
Debt	0	0
Total liabilities measured at fair value	0	0
Fair Value \| Level 2 \| Money market and other funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market and other funds	0	0
Fair Value \| Level 2 \| Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Corporate debt securities	0	663
Fair Value \| Level 3
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value	0	0
Contingent consideration	9,296	9,094
Debt	0	0
Total liabilities measured at fair value	9,296	9,094
Fair Value \| Level 3 \| Money market and other funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market and other funds	0	0
Fair Value \| Level 3 \| Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Corporate debt securities	0	0
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value	10,391	11,076
Contingent consideration	9,296	9,094
Debt	1,678,753	1,579,021
Total liabilities measured at fair value	1,688,049	1,588,115
Carrying Value \| Money market and other funds
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market and other funds	10,391	10,413
Carrying Value \| Corporate debt securities
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Corporate debt securities	$ 0	$ 663

Fair value portion of probable future economic benefits obtained or controlled by an entity as a result of past transactions or events.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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- Definition

Amount of liability recognized arising from contingent consideration in a business combination.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 50
-Paragraph 1
-Subparagraph (c)(1)
-URI http://asc.fasb.org/extlink&oid=120321790&loc=d3e6927-128479

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 35
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=116859824&loc=d3e6819-128478

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 30
-Section 25
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=6911189&loc=d3e6408-128476

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- Definition

Fair value portion of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates.

+ References

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+ References

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- Definition

Fair value of financial obligations, including, but not limited to, debt instruments, derivative liabilities, federal funds purchased and sold under agreements to repurchase, securities loaned or sold under agreements to repurchase, financial instruments sold not yet purchased, guarantees, line of credit, loans and notes payable, servicing liability, and trading liabilities.

+ References

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- Definition

Fair value portion of investment securities, including, but not limited to, marketable securities, derivative financial instruments, and investments accounted for under the equity method.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=123874694&loc=d3e19207-110258

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- Definition

The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

+ References

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