Fair Value Measurements - Schedule of Financial Assets At Fair Value (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	$ 7,499	$ 4,558
Deferred compensation investments	10,104	8,843
Interest Rate Swaps and Collars
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of derivative instruments, asset derivatives	4,731
Interest Rate Swap Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of derivative instruments, asset derivatives		3,884
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	5,594	2,586
Deferred compensation investments	3,377	1,450
Significant Other Observable Inputs (Level 2)
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Short-term investments	1,905	1,972
Deferred compensation investments	6,727	7,393
Significant Other Observable Inputs (Level 2) | Interest Rate Swaps and Collars
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of derivative instruments, asset derivatives	$ 4,731
Significant Other Observable Inputs (Level 2) | Interest Rate Swap Assets
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair value of derivative instruments, asset derivatives		$ 3,884