Fair Value Measurements (Financial assets and liabilities measured at fair value on a recurring basis) (Details) - Fair Value, Measurements, Recurring [Member] - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
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	$ 13,710	$ 12,360
Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Intangible and other long-term assets, net		8,579
Non Qualified Deferred Compensation Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable	1,157	1,115
Other long-term liabilities	20,250	18,489
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	369	368
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	13,341	11,992
Level 2 [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Intangible and other long-term assets, net		8,579
Level 2 [Member] | Non Qualified Deferred Compensation Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable	1,157	1,115
Other long-term liabilities	20,250	18,489
Level 3 [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
Level 3 [Member] | Interest Rate Swap [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Intangible and other long-term assets, net
Level 3 [Member] | Non Qualified Deferred Compensation Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Accounts payable
Other long-term liabilities