Investment Income (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Investment Income [Abstract]
Interest and dividend income	$ 3,753,000	$ 2,184,000	$ 3,471,000
Investment gain	9,780,000	1,071,000	3,010,000
Equity earnings (loss)	(522,000)	(864,000)	367,000
Total investment income	13,011,000	2,391,000	6,848,000
Gain associated in connection with previously written-off investment	$ 9,800,000