Fair Value Measurements (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Trading equity securities [Abstract]
SERP money market fund	$ 998,000		$ 998,000		$ 996,000
SERP mutual funds	2,248,000		2,248,000		1,835,000
Preferred stocks	676,000		676,000		720,000
Short-term investment in mutual funds	15,536,000		15,536,000
Trading debt securities [Abstract]
Corporate bonds	5,042,000		5,042,000		4,251,000
Municipal bonds	1,449,000		1,449,000		2,406,000
Floating rate notes	569,000		569,000		749,000
U.S. Treasury bonds and bills	472,000		472,000		200,000
Other	952,000		952,000		409,000
Short-term derivative financial instruments	216,000		216,000
Total financial assets	28,158,000		28,158,000		11,566,000
Financial Liabilities [Abstract]
SERP liabilities	7,394,000		7,394,000		6,674,000
Short-term derivative financial instruments					145,000
Total financial liabilities	7,394,000		7,394,000		6,819,000
Investments included in Level 2 were transferred to Level 1	951,000		951,000
Trading debt securities due to mature within twelve months	807,000		807,000		1,334,000
Net unrealized gains (losses) incurred	656,000	105,000	553,000	273,000
Level 1 [Member]
Trading equity securities [Abstract]
SERP money market fund	998,000		998,000		996,000
SERP mutual funds	2,248,000		2,248,000		1,835,000
Preferred stocks	676,000		676,000		720,000
Short-term investment in mutual funds	15,536,000		15,536,000
Trading debt securities [Abstract]
Corporate bonds	3,815,000		3,815,000		3,342,000
Municipal bonds	0		0		1,449,000
Floating rate notes	102,000		102,000		749,000
U.S. Treasury bonds and bills	472,000		472,000		200,000
Other	0		0		0
Short-term derivative financial instruments	0		0
Total financial assets	23,847,000		23,847,000		9,291,000
Financial Liabilities [Abstract]
SERP liabilities	0		0		0
Short-term derivative financial instruments					0
Total financial liabilities	0		0		0
Level 2 [Member]
Trading equity securities [Abstract]
SERP money market fund	0		0		0
SERP mutual funds	0		0		0
Preferred stocks	0		0		0
Short-term investment in mutual funds	0		0
Trading debt securities [Abstract]
Corporate bonds	1,227,000		1,227,000		909,000
Municipal bonds	1,449,000		1,449,000		957,000
Floating rate notes	467,000		467,000		0
U.S. Treasury bonds and bills	0		0		0
Other	952,000		952,000		409,000
Short-term derivative financial instruments	216,000		216,000
Total financial assets	4,311,000		4,311,000		2,275,000
Financial Liabilities [Abstract]
SERP liabilities	7,394,000		7,394,000		6,674,000
Short-term derivative financial instruments					145,000
Total financial liabilities	$ 7,394,000		$ 7,394,000		$ 6,819,000