Significant Accounting Policies (Details 3) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Investment in Marketable Securities
Marketable securities	$ 32,049,000				$ 21,429,000				$ 32,049,000	$ 21,429,000
Net proceeds on sale of marketable securities									0	6,800,000	6,200,000
Realized gain (loss) on investment in marketable securities	0	0	(8,000)	(57,000)	2,703,000	2,237,000	0	0	0	4,900,000	4,500,000
Proceeds from sale and maturity of marketable securities									2,370,000	11,070,000	40,248,000
Commercial mortgage-backed securities
Investment in Marketable Securities
Cost basis	23,000,000				13,700,000				23,000,000	13,700,000
Rake bonds
Investment in Marketable Securities
Cost basis	3,600,000				3,700,000				3,600,000	3,700,000
Realized gain (loss) on investment in marketable securities											400,000
Proceeds from sale and maturity of marketable securities											22,500,000
Level 1 | Equity marketable securities
Investment in Marketable Securities
Marketable securities	4,307,000				2,202,000				4,307,000	2,202,000
Level 2 | Commercial mortgage-backed securities
Investment in Marketable Securities
Marketable securities	24,419,000				15,575,000				24,419,000	15,575,000
Level 3 | Rake bonds
Investment in Marketable Securities
Marketable securities	3,323,000				3,652,000				3,323,000	3,652,000
Fair Value
Investment in Marketable Securities
Marketable securities	$ 32,049,000				$ 21,429,000				$ 32,049,000	$ 21,429,000