Fair Value Measurements (Summary of Financial Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total debt	$ 885,500	$ 1,084,711
Non-Qualified Deferred Compensation Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Intangible and other long-term assets, net	14,686	13,306
Non Qualified Deferred Compensation Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable	1,224	1,138
Other long-term liabilities	21,974	19,766
Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Total debt	885,500	1,084,711
Level 1 [Member] | Non-Qualified Deferred Compensation Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Intangible and other long-term assets, net		376
Level 2 [Member] | Non-Qualified Deferred Compensation Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Intangible and other long-term assets, net	14,686	12,930
Level 2 [Member] | Non Qualified Deferred Compensation Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable	1,224	1,138
Other long-term liabilities	$ 21,974	$ 19,766