Fair Value Measurements (Details) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011
Trading equity securities:
SERP money market fund	$ 993,000		$ 993,000		$ 989,000
SERP mutual funds	2,054,000		2,054,000		1,732,000
Preferred stocks	717,000		717,000		441,000
Trading debt securities:
Corporate bonds	3,514,000		3,514,000		3,887,000
Municipal bonds	3,013,000		3,013,000		3,091,000
Floating rate notes	1,118,000		1,118,000		330,000
U.S. Treasury bill	250,000		250,000		250,000
Other government bonds	278,000		278,000		343,000
Derivative financial instruments					307,000
Total financial assets	11,937,000		11,937,000		11,370,000
Financial Liabilities:
SERP liabilities	6,342,000		6,342,000		6,076,000
Derivative financial instruments	129,000		129,000		50,000
Total financial liabilities	6,471,000		6,471,000		6,126,000
Investments reclassified as Level 1	98,000		98,000
Investments reclassified as Level 2	1,110,000		1,110,000
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amortized Cost	11,643,000		11,643,000		10,921,000
Gross Unrealized Gains			389,000		292,000
Gross Unrealized Losses			95,000		150,000
Fair Value (Net Carrying Amount)	11,937,000		11,937,000		11,063,000
Trading debt securities due to mature within twelve months	2,024,000		2,024,000		1,324,000
Net unrealized gains (losses) incurred	(90,353)	70,000	162,000	194,000
Trading equity securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amortized Cost	3,606,000		3,606,000		3,160,000
Gross Unrealized Gains			171,000		81,000
Gross Unrealized Losses			13,000		79,000
Fair Value (Net Carrying Amount)	3,764,000		3,764,000		3,162,000
Trading debt securities [Member]
Schedule of Trading Securities and Other Trading Assets [Line Items]
Amortized Cost	8,037,000		8,037,000		7,761,000
Gross Unrealized Gains			218,000		211,000
Gross Unrealized Losses			82,000		71,000
Fair Value (Net Carrying Amount)	8,173,000		8,173,000		7,901,000
Level 1 [Member]
Trading equity securities:
SERP money market fund	993,000		993,000		989,000
SERP mutual funds	2,054,000		2,054,000		1,732,000
Preferred stocks	717,000		717,000		441,000
Trading debt securities:
Corporate bonds	2,071,000		2,071,000		1,649,000
Municipal bonds	1,246,000		1,246,000		211,000
Floating rate notes	695,000		695,000		97,000
U.S. Treasury bill	250,000		250,000		250,000
Other government bonds	0		0		0
Derivative financial instruments					0
Total financial assets	8,026,000		8,026,000		5,369,000
Financial Liabilities:
SERP liabilities	6,342,000		6,342,000		6,076,000
Derivative financial instruments	0		0		0
Total financial liabilities	6,342,000		6,342,000		6,076,000
Level 2 [Member]
Trading equity securities:
SERP money market fund	0		0		0
SERP mutual funds	0		0		0
Preferred stocks	0		0		0
Trading debt securities:
Corporate bonds	1,443,000		1,443,000		2,238,000
Municipal bonds	1,767,000		1,767,000		2,880,000
Floating rate notes	423,000		423,000		233,000
U.S. Treasury bill	0		0		0
Other government bonds	278,000		278,000		343,000
Derivative financial instruments					307,000
Total financial assets	3,911,000		3,911,000		6,001,000
Financial Liabilities:
SERP liabilities	0		0		0
Derivative financial instruments	129,000		129,000		50,000
Total financial liabilities	129,000		129,000		50,000
Level 3 [Member]
Trading equity securities:
SERP money market fund	0		0		0
SERP mutual funds	0		0		0
Preferred stocks	0		0		0
Trading debt securities:
Corporate bonds	0		0		0
Municipal bonds	0		0		0
Floating rate notes	0		0		0
U.S. Treasury bill	0		0		0
Other government bonds	0		0		0
Derivative financial instruments					0
Total financial assets	0		0		0
Financial Liabilities:
SERP liabilities	0		0		0
Derivative financial instruments	0		0		0
Total financial liabilities	$ 0		$ 0		$ 0