Financial Instruments FInancial Instruments (Details) - USD ($) $ in Thousands	Jun. 30, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 23,176	$ 23,737
Deferred Compensation Liability, Current and Noncurrent	28,772	29,155
Financial and Nonfinancial Liabilities, Fair Value Disclosure	32,350	30,737
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	23,176	23,737
Deferred Compensation Liability, Current and Noncurrent	28,772	29,155
Financial and Nonfinancial Liabilities, Fair Value Disclosure	32,350	30,737
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	0	0
Deferred Compensation Liability, Current and Noncurrent	0	0
Financial and Nonfinancial Liabilities, Fair Value Disclosure	0	0
Interest Rate Swap No. 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	851	353
Interest Rate Swap No. 2 [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	0	0
Interest Rate Swap No. 2 [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	851	353
Interest Rate Swap No. 2 [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	0	0
Interest Rate Swap No. 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	2,727	1,229
Interest Rate Swap No. 1 [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	0	0
Interest Rate Swap No. 1 [Member] | Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	2,727	1,229
Interest Rate Swap No. 1 [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	$ 0	$ 0