Investments Available-for-Sale Invsetments (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2017		Sep. 30, 2016	Sep. 30, 2017		Sep. 30, 2016	Dec. 31, 2016
Available-for-sale Investments [Abstract]
Cost		$ 24,608			$ 24,608			$ 33,891
Gross Unrealized Gains		1,820			1,820			1,962
Gross Unrealized Losses		(241)	[1]		(241)	[1]		(457)	[2]
Fair Value		26,187			26,187			35,396
Available-for-sale investments in an unrealized loss position		4,288			4,288			18,521
Proceeds from Investing Activities [Abstract]
Proceeds from sales		4,444		$ 9,788	24,354		$ 15,207
Gross realized gains		336		983	650		1,454
Gross realized losses		(101)		$ (39)	(297)		$ (382)
Preferred securities
Available-for-sale Investments [Abstract]
Cost		1,086			1,086			1,020
Gross Unrealized Gains		38			38			13
Gross Unrealized Losses		(2)	[1]		(2)	[1]		(22)	[2]
Fair Value		1,122			1,122			1,011
Common stocks
Available-for-sale Investments [Abstract]
Cost		6,428			6,428			4,639
Gross Unrealized Gains		431			431			194
Gross Unrealized Losses		(205)	[1]		(205)	[1]		(325)	[2]
Fair Value		6,654			6,654			4,508
Company-sponsored funds
Available-for-sale Investments [Abstract]
Cost		13,376			13,376			28,232
Gross Unrealized Gains		1,319			1,319			1,755
Gross Unrealized Losses		(21)	[1]		(21)	[1]		(110)	[2]
Fair Value		14,674			14,674			$ 29,877
Fixed income securities
Available-for-sale Investments [Abstract]
Cost		3,618			3,618
Gross Unrealized Gains		16			16
Gross Unrealized Losses	[1]	(13)			(13)
Fair Value		3,621			3,621
Other Investments
Available-for-sale Investments [Abstract]
Cost		100			100
Gross Unrealized Gains		16			16
Gross Unrealized Losses	[1]	0			0
Fair Value		$ 116			$ 116

[1] At September 30, 2017, there were no securities with material unrealized losses continuously for a period of more than 12 months.

[2] At December 31, 2016, there were no securities with unrealized losses continuously for a period of more than 12 months.