Fair Value (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Investments in securities [Abstract]
Total investments in securities	$ 33,789	$ 36,790
Fair Value, Transfers between Level 1 and Level 2 and between Level 1 and Level 3 [Abstract]
Level 1 to level 2 transfers	0	0
Level 2 to level 1 transfers	0	0
Level 1 to level 3 transfers	0	0
Level 3 to level 1 transfers	0	0
Recurring Basis [Member]
Assets [Abstract]
Cash equivalents	40,905	17,475
Investments in securities [Abstract]
AFS - Common stocks		36,637
AFS - Closed-end Funds		108
Trading - Common stocks	32,414	34
Trading - Closed-end funds	38
Trading - Mutual funds	1,337	11
Total investments in securities	33,789	36,790
Total assets at fair value	74,694	54,265
Recurring Basis [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Assets [Abstract]
Cash equivalents	40,905	17,475
Investments in securities [Abstract]
AFS - Common stocks		36,637
AFS - Closed-end Funds		108
Trading - Common stocks	32,414	34
Trading - Closed-end funds	38
Trading - Mutual funds	1,337	11
Total investments in securities	33,789	36,790
Total assets at fair value	74,694	54,265
Recurring Basis [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets [Abstract]
Cash equivalents	0	0
Investments in securities [Abstract]
AFS - Common stocks		0
AFS - Closed-end Funds		0
Trading - Common stocks	0	0
Trading - Closed-end funds	0
Trading - Mutual funds	0	0
Total investments in securities	0	0
Total assets at fair value	0	0
Recurring Basis [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets [Abstract]
Cash equivalents	0	0
Investments in securities [Abstract]
AFS - Common stocks		0
AFS - Closed-end Funds		0
Trading - Common stocks	0	0
Trading - Closed-end funds	0
Trading - Mutual funds	0	0
Total investments in securities	0	0
Total assets at fair value	$ 0	$ 0