Fair Value Measurements (Details) - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended |
Sep. 30, 2016 | Dec. 31, 2015 |
Financial Liabilities [Abstract] | | |
Net unrealized gains or losses incurred | $ 94 | $ (429) |
Measured at Fair Value on a Recurring Basis [Member] | | |
Financial Assets [Abstract] | | |
Derivative financial instruments | | 1,265 |
Total financial assets | 14,807 | 14,344 |
Financial Liabilities [Abstract] | | |
SERP liabilities | 7,218 | 5,869 |
Derivative financial instruments | 592 | 22 |
Total financial liabilities | 7,810 | 5,891 |
Measured at Fair Value on a Recurring Basis [Member] | SERP Money Market Fund [Member] | | |
Financial Assets [Abstract] | | |
Investments | 90 | 445 |
Measured at Fair Value on a Recurring Basis [Member] | SERP Mutual Funds [Member] | | |
Financial Assets [Abstract] | | |
Investments | 3,229 | 2,864 |
Measured at Fair Value on a Recurring Basis [Member] | Preferred Stocks [Member] | | |
Financial Assets [Abstract] | | |
Investments | 620 | 742 |
Measured at Fair Value on a Recurring Basis [Member] | Corporate Bonds [Member] | | |
Financial Assets [Abstract] | | |
Investments | 5,109 | 3,897 |
Measured at Fair Value on a Recurring Basis [Member] | Municipal Bonds [Member] | | |
Financial Assets [Abstract] | | |
Investments | 2,441 | 1,811 |
Measured at Fair Value on a Recurring Basis [Member] | Floating Rate Notes [Member] | | |
Financial Assets [Abstract] | | |
Investments | 98 | 84 |
Measured at Fair Value on a Recurring Basis [Member] | U.S. Treasury Bills [Member] | | |
Financial Assets [Abstract] | | |
Investments | | 404 |
Measured at Fair Value on a Recurring Basis [Member] | Asset Backed Securities [Member] | | |
Financial Assets [Abstract] | | |
Investments | 694 | |
Measured at Fair Value on a Recurring Basis [Member] | Saving Bonds [Member] | | |
Financial Assets [Abstract] | | |
Investments | | 77 |
Measured at Fair Value on a Recurring Basis [Member] | Other [Member] | | |
Financial Assets [Abstract] | | |
Investments | 2,526 | 2,755 |
Measured at Fair Value on a Recurring Basis [Member] | Level 1 [Member] | | |
Financial Assets [Abstract] | | |
Derivative financial instruments | | 0 |
Total financial assets | 9,146 | 8,372 |
Financial Liabilities [Abstract] | | |
SERP liabilities | 0 | 0 |
Derivative financial instruments | 0 | 0 |
Total financial liabilities | 0 | 0 |
Measured at Fair Value on a Recurring Basis [Member] | Level 1 [Member] | SERP Money Market Fund [Member] | | |
Financial Assets [Abstract] | | |
Investments | 90 | 445 |
Measured at Fair Value on a Recurring Basis [Member] | Level 1 [Member] | SERP Mutual Funds [Member] | | |
Financial Assets [Abstract] | | |
Investments | 3,229 | 2,864 |
Measured at Fair Value on a Recurring Basis [Member] | Level 1 [Member] | Preferred Stocks [Member] | | |
Financial Assets [Abstract] | | |
Investments | 620 | 742 |
Measured at Fair Value on a Recurring Basis [Member] | Level 1 [Member] | Corporate Bonds [Member] | | |
Financial Assets [Abstract] | | |
Investments | 5,109 | 3,756 |
Measured at Fair Value on a Recurring Basis [Member] | Level 1 [Member] | Municipal Bonds [Member] | | |
Financial Assets [Abstract] | | |
Investments | 0 | 0 |
Measured at Fair Value on a Recurring Basis [Member] | Level 1 [Member] | Floating Rate Notes [Member] | | |
Financial Assets [Abstract] | | |
Investments | 98 | 84 |
Measured at Fair Value on a Recurring Basis [Member] | Level 1 [Member] | U.S. Treasury Bills [Member] | | |
Financial Assets [Abstract] | | |
Investments | | 404 |
Measured at Fair Value on a Recurring Basis [Member] | Level 1 [Member] | Asset Backed Securities [Member] | | |
Financial Assets [Abstract] | | |
Investments | 0 | |
Measured at Fair Value on a Recurring Basis [Member] | Level 1 [Member] | Saving Bonds [Member] | | |
Financial Assets [Abstract] | | |
Investments | | 77 |
Measured at Fair Value on a Recurring Basis [Member] | Level 1 [Member] | Other [Member] | | |
Financial Assets [Abstract] | | |
Investments | 0 | 0 |
Measured at Fair Value on a Recurring Basis [Member] | Level 2 [Member] | | |
Financial Assets [Abstract] | | |
Derivative financial instruments | | 1,265 |
Total financial assets | 5,661 | 5,972 |
Financial Liabilities [Abstract] | | |
SERP liabilities | 7,218 | 5,869 |
Derivative financial instruments | 592 | 22 |
Total financial liabilities | 7,810 | 5,891 |
Measured at Fair Value on a Recurring Basis [Member] | Level 2 [Member] | SERP Money Market Fund [Member] | | |
Financial Assets [Abstract] | | |
Investments | 0 | 0 |
Measured at Fair Value on a Recurring Basis [Member] | Level 2 [Member] | SERP Mutual Funds [Member] | | |
Financial Assets [Abstract] | | |
Investments | 0 | 0 |
Measured at Fair Value on a Recurring Basis [Member] | Level 2 [Member] | Preferred Stocks [Member] | | |
Financial Assets [Abstract] | | |
Investments | 0 | 0 |
Measured at Fair Value on a Recurring Basis [Member] | Level 2 [Member] | Corporate Bonds [Member] | | |
Financial Assets [Abstract] | | |
Investments | 0 | 141 |
Measured at Fair Value on a Recurring Basis [Member] | Level 2 [Member] | Municipal Bonds [Member] | | |
Financial Assets [Abstract] | | |
Investments | 2,441 | 1,811 |
Measured at Fair Value on a Recurring Basis [Member] | Level 2 [Member] | Floating Rate Notes [Member] | | |
Financial Assets [Abstract] | | |
Investments | 0 | 0 |
Measured at Fair Value on a Recurring Basis [Member] | Level 2 [Member] | U.S. Treasury Bills [Member] | | |
Financial Assets [Abstract] | | |
Investments | | 0 |
Measured at Fair Value on a Recurring Basis [Member] | Level 2 [Member] | Asset Backed Securities [Member] | | |
Financial Assets [Abstract] | | |
Investments | 694 | |
Measured at Fair Value on a Recurring Basis [Member] | Level 2 [Member] | Saving Bonds [Member] | | |
Financial Assets [Abstract] | | |
Investments | | 0 |
Measured at Fair Value on a Recurring Basis [Member] | Level 2 [Member] | Other [Member] | | |
Financial Assets [Abstract] | | |
Investments | $ 2,526 | $ 2,755 |