Fair Value (Narrative) (Details) (USD $)	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Fair value of public equity portfolio	$ 103,866,000		$ 96,890,000
Transfers between Level 1 and Level 2	0
Transfers from level 3	7,887,000	0
Available For Sale Securities Debt Securities Market Value	5,226,919,000		5,293,411,000
Private Placement [Member] | Unavailability Of Prices [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Number of securities	1
Available For Sale Securities Debt Securities Market Value	$ 6,125,000