Fair Value Measurements - Fair Values of Financial Instruments Measured On Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value	$ 11,076	$ 418,334
Contingent consideration	9,094	37,887
Long-term debt	1,960,527	1,833,062
Total liabilities measured at fair value	1,969,621	1,870,949
Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value	11,076	418,334
Contingent consideration	9,094	37,887
Long-term debt	1,579,021	1,448,461
Total liabilities measured at fair value	1,588,115	1,486,348
Money market and other funds | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market and other funds	10,413	395,664
Money market and other funds | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market and other funds	10,413	395,664
Corporate debt securities | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Corporate debt securities	663	22,670
Corporate debt securities | Carrying Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Corporate debt securities	663	22,670
Level 1 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value	10,413	395,664
Contingent consideration	0	0
Long-term debt	1,960,527	0
Total liabilities measured at fair value	1,960,527	0
Level 1 | Money market and other funds | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market and other funds	10,413	395,664
Level 1 | Corporate debt securities | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Corporate debt securities	0	0
Level 2
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	2,000,000	1,800,000
Level 2 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value	663	623
Contingent consideration	0	0
Long-term debt	0	1,833,062
Total liabilities measured at fair value	0	1,833,062
Level 2 | Money market and other funds | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market and other funds	0	0
Level 2 | Corporate debt securities | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Corporate debt securities	663	623
Level 3 | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Total assets measured at fair value	0	22,047
Contingent consideration	9,094	37,887
Long-term debt	0	0
Total liabilities measured at fair value	9,094	37,887
Level 3 | Money market and other funds | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Money market and other funds	0	0
Level 3 | Corporate debt securities | Fair Value
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Corporate debt securities	$ 0	$ 22,047