Financial Instruments FInancial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, Fair Value Disclosure	$ 22,582	$ 23,737
Deferred Compensation Liability, Current and Noncurrent	27,967	29,155
Financial and Nonfinancial Liabilities, Fair Value Disclosure	30,956	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	22,582	23,737
Deferred Compensation Liability, Current and Noncurrent	27,967	29,155
Financial and Nonfinancial Liabilities, Fair Value Disclosure	30,956	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	754	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	754	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	2,235	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	2,235	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