Fair Value of Financial Instruments Liabilities Fair Value Measurement on a Recurring Basis (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation liability	$ 1,424	$ 1,156
Interest rate swap asset	6,002	5,091
Interest rate swap liability	801	10
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation liability	0	0
Interest rate swap asset	0	0
Interest rate swap liability	0	0
Fair Value, Inputs, Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation liability	0	0
Interest rate swap asset	0	0
Interest rate swap liability	0	0
Fair Value, Measurements, Recurring | Fair Value, Inputs, Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Deferred compensation liability	1,424	1,156
Interest rate swap asset	6,002	5,091
Interest rate swap liability	$ 801	$ 10