Fair Value of Financial Instruments Reconciliation of Fair Value of recurring Level 3 fair value measurements (tables) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Mar. 31, 2018	Dec. 31, 2016
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Alternative Investment	$ 26,015	$ 32,211
Investments	59,904	79,839
Payments for (Proceeds from) Other Investing Activities	0	171
Loss on change in fair value of limited liability investments	(7,393)	(1,832)
Real estate investments, at fair value (cost of $10,225 and 10,225, respectively)	10,662	10,662		$ 10,662
Transfer from Investments	0	0
Proceeds from (Payments for) Other Financing Activities	0	113
Contingent consideration benefit	0	(212)
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Alternative Investment	4,124	1,397		939
Investments	14,786	12,059
Real estate investments, at fair value (cost of $10,225 and 10,225, respectively)	10,662		$ 10,662
Business Combination, Contingent Consideration, Liability	0	0		$ 325
Fair Value, Net Asset (Liability)	14,786	12,059
Incentive Distribution, Distribution	(386)	(86)
Other than Securities Investment [Member] | Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments	14,786	12,059
Payments for (Proceeds from) Other Investing Activities	1,580	664
Loss on change in fair value of limited liability investments	1,533	(120)
Other Security Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Investments	$ 52,024	$ 65,875