Fair Value Disclosures (Quantitative Information About Level 3 Fair Value Measurements) (Details) - Significant Unobservable Inputs (Level 3) [Member] - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
CLOs [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 14,250	$ 4,485
CLOs [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	8.90%	11.80%
Duration	4 years 3 months 18 days	4 years 3 months 18 days
CLOs [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	14.00%	19.10%
Duration	12 years 7 months 6 days	4 years 6 months
CLOs [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Yield	13.20%	13.80%
Duration	10 years 4 months 24 days	4 years 4 months 24 days
Default rate	2.00%	2.00%
Equity securities [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
Fair Value	$ 2,066	$ 2,066
Equity securities [Member] | Minimum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
EBITDA Multiple	7.6	7.6
Equity securities [Member] | Maximum [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
EBITDA Multiple	9.2	9.2
Equity securities [Member] | Weighted Average [Member]
Fair Value Inputs, Assets, Quantitative Information [Line Items]
EBITDA Multiple	8.00	8.00