Fair Value Measurement (Carrying Values And Fair Values Of The Company's Financial Instruments) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Amount	$ 2,849,307	$ 3,096,229
Estimated Fair Value	2,907,379	3,152,553
Term-A Facility [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Amount	669,878	723,560
Estimated Fair Value	665,719	724,303
4.75% Senior Notes Due December 2022 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Amount	398,230	595,813
Estimated Fair Value	400,500	605,250
5.00% Senior Notes Due April 2024 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Amount	991,074	988,609
Estimated Fair Value	1,015,000	1,020,000
4.75% Senior Notes Due 2025 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Carrying Amount	790,125	788,247
Estimated Fair Value	$ 826,160	$ 803,000