Fair Value of Assets and Liabilities (Fair Value Assets Measured on Non-Recurring Basis) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Private Equity Funds [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value Assets Carrying Value Prior To Impairment	[1]	$ 0	$ 106
Fair Value Assets Gains Losses	[1]	0	(531)
Partnership Interest [Member]
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Fair Value Assets Carrying Value Prior To Impairment	[2]	4,596	4,656
Fair Value Assets Gains Losses	[2]	$ (3,200)	$ (7,204)

[1] The fair value of the Company’s private equity investments is based on external valuation models.

[2] The impaired limited partnership interests presented above were accounted for using the cost method. Impairments on these cost method investments were recognized at estimated fair value determined using the net asset values of the Company’s ownership interest as provided in the financial statements of the investees. The market for these investments has limited activity and price transparency