Financial Instruments (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation trust assets (1)	$ 25,530	$ 23,737
Deferred Compensation Liability, Current	31,672	29,155
Deferred compensation plan	32,718	30,737
Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation trust assets (1)	0	0
Deferred Compensation Liability, Current	0	0
Deferred compensation plan	0	0
Fair Value, Inputs, Level 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation trust assets (1)	25,530	23,737
Deferred Compensation Liability, Current	31,672	29,155
Deferred compensation plan	32,718	30,737
Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Deferred compensation trust assets (1)	0	0
Deferred Compensation Liability, Current	0	0
Deferred compensation plan	0	0
Interest Rate Swap No. 2 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	211	353
Interest Rate Swap No. 2 [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [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, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative, Term of Contract	5 years
Interest Rate Derivative Liabilities, at Fair Value	$ 211	353
Interest Rate Swap No. 2 [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	0	0
Interest Rate Swap No. 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	835	1,229
Interest Rate Swap No. 1 [Member] | Fair Value, Inputs, Level 1 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [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, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Derivative, Term of Contract	10 years
Interest Rate Derivative Liabilities, at Fair Value	$ 835	1,229
Interest Rate Swap No. 1 [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Interest Rate Derivative Liabilities, at Fair Value	$ 0	$ 0