Fair Value Measurements (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Dec. 31, 2012
Trading equity securities [Abstract]
SERP money market fund	$ 997,000		$ 997,000		$ 996,000
SERP mutual funds	1,904,000		1,904,000		1,835,000
Preferred stocks	714,000		714,000		720,000
Mutual funds	14,901,000		14,901,000
Trading debt securities [Abstract]
Corporate bonds	4,838,000		4,838,000		4,251,000
Municipal bonds	1,739,000		1,739,000		2,406,000
Floating rate notes	575,000		575,000		749,000
U.S. Treasury bill	470,000		470,000		200,000
Other	980,000		980,000		409,000
Derivative financial instruments	1,001,000		1,001,000
Total financial assets	28,119,000		28,119,000		11,566,000
Financial Liabilities [Abstract]
SERP liabilities	6,949,000		6,949,000		6,674,000
Short-term derivative financial instruments					145,000
Total financial liabilities	6,949,000		6,949,000		6,819,000
Trading debt securities due to mature within twelve months	1,087,000		1,087,000		1,334,000
Trading equity securities in short-term investment	14,901,000		14,901,000		0
Net unrealized gains (losses) incurred	(251,000)	(90,000)	(114,000)	162,000
Investments included in Level 1 were transferred to Level 2	594,000		594,000
Level 1 [Member]
Trading equity securities [Abstract]
SERP money market fund	997,000		997,000		996,000
SERP mutual funds	1,904,000		1,904,000		1,835,000
Preferred stocks	714,000		714,000		720,000
Mutual funds	14,901,000		14,901,000		0
Trading debt securities [Abstract]
Corporate bonds	3,670,000		3,670,000		3,342,000
Municipal bonds	506,000		506,000		1,449,000
Floating rate notes	303,000		303,000		749,000
U.S. Treasury bill	470,000		470,000		200,000
Other	0		0		0
Derivative financial instruments	0		0		0
Total financial assets	23,465,000		23,465,000		9,291,000
Financial Liabilities [Abstract]
SERP liabilities	0		0		0
Short-term derivative financial instruments	0		0		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
Mutual funds	0		0
Trading debt securities [Abstract]
Corporate bonds	1,168,000		1,168,000		909,000
Municipal bonds	1,233,000		1,233,000		957,000
Floating rate notes	272,000		272,000		0
U.S. Treasury bill	0		0		0
Other	980,000		980,000		409,000
Derivative financial instruments	1,001,000		1,001,000		0
Total financial assets	4,654,000		4,654,000		2,275,000
Financial Liabilities [Abstract]
SERP liabilities	6,949,000		6,949,000		6,674,000
Short-term derivative financial instruments					145,000
Total financial liabilities	$ 6,949,000		$ 6,949,000		$ 6,819,000