Investments (Other Investment Portfolio by Strategy and the Remaining Commitment Amount Associated With Each Strategy) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Carrying Value	$ 85,146	$ 99,203
Alternative Investments [Member]
Carrying Value	74,168	92,968
Remaining Commitment	74,278
Other Investments [Member]
Carrying Value	85,146	99,203
Remaining Commitment	76,547
Secondary Private Equity [Member] | Alternative Investments [Member]
Carrying Value	17,503	21,807
Remaining Commitment	7,095
Private Equity [Member] | Alternative Investments [Member]
Carrying Value	15,792	20,126
Remaining Commitment	23,826
Energy/Power Generation [Member] | Alternative Investments [Member]
Carrying Value	11,643	14,445
Remaining Commitment	16,857
Real Estate [Member] | Alternative Investments [Member]
Carrying Value	8,854	11,452
Remaining Commitment	9,919
Mezzanine Financing [Member] | Alternative Investments [Member]
Carrying Value	6,948	9,853
Remaining Commitment	13,383
Distressed debt [Member] | Alternative Investments [Member]
Carrying Value	6,889	8,679
Remaining Commitment	3,048
Venture Capital [Member] | Alternative Investments [Member]
Carrying Value	6,539	6,606
Remaining Commitment	150
Other Securities [Member]
Carrying Value	10,978	$ 6,235
Remaining Commitment	$ 2,269