Investment in Securities, Summary of Cost, Gross Unrealized Gains, Gross Unrealized Losses and Fair Value (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016	Dec. 31, 2016
Available-for-sale Securities, Fair Value to Amortized Cost Basis [Abstract]
Cost	$ 21,418,000	$ 17,649,000	$ 21,418,000	$ 17,649,000	$ 18,838,000
Gross unrealized gains	20,011,000	15,224,000	20,011,000	15,224,000	18,393,000
Gross unrealized losses	0	0	0	0	0
Fair value	41,429,000	32,873,000	41,429,000	32,873,000	37,231,000
Changes in net unrealized gain (loss), net of tax	2,321,000	506,000	1,019,000	323,000
Proceeds from sale of investment available for sale	321,000	0	321,000	408,000
Gross realized gains on sale of investment available for sale	20,000	0	20,000	4,000
Gross realized losses on sale of investment available for sale	0	0	0	0
Common Stock [Member]
Available-for-sale Securities, Fair Value to Amortized Cost Basis [Abstract]
Cost	21,319,000	17,649,000	21,319,000	17,649,000	18,739,000
Gross unrealized gains	19,996,000	15,224,000	19,996,000	15,224,000	18,392,000
Gross unrealized losses	0	0	0	0	0
Fair value	41,315,000	32,873,000	41,315,000	32,873,000	37,131,000
Closed-end Funds [Member]
Available-for-sale Securities, Fair Value to Amortized Cost Basis [Abstract]
Cost	99,000	0	99,000	0	99,000
Gross unrealized gains	15,000		15,000		1,000
Gross unrealized losses	0		0		0
Fair value	$ 114,000	$ 0	$ 114,000	$ 0	$ 100,000