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Investments (Other Investment Portfolio by Strategy and the Remaining Commitment Amount Associated With Each Strategy) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Carrying Value	$ 178,938	$ 132,268
Other Investment Portfolio [Member]
Carrying Value	178,938	132,268
Remaining Commitment	202,270	220,999
Maximum Exposure to Loss	381,208	353,267
Alternative Investments [Member]
Carrying Value	153,896	115,373
Remaining Commitment	202,270	220,999
Maximum Exposure to Loss	356,166	336,372
Private Equity [Member] | Alternative Investments [Member]
Carrying Value	84,352	52,251
Remaining Commitment	93,688	99,026
Maximum Exposure to Loss	178,040	151,277
Private Credit Funds [Member] | Alternative Investments [Member]
Carrying Value	41,682	37,743
Remaining Commitment	81,453	94,959
Maximum Exposure to Loss	123,135	132,702
Real Assets [Member] | Alternative Investments [Member]
Carrying Value	27,862	25,379
Remaining Commitment	27,129	27,014
Maximum Exposure to Loss	54,991	52,393
Other Securities [Member]
Carrying Value	25,042	16,895
Remaining Commitment	0	0
Maximum Exposure to Loss	$ 25,042	$ 16,895

X

- Definition

This item represents contractual obligations to invest additional amounts on our other investment portfolio. These additional investments may or may not be required.

+ References

No definition available.

+ Details

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- Definition

Amount of investments classified as other.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(f,g))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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- Definition

The reporting entity's maximum amount of exposure to loss as a result of its involvement with the Variable Interest Entity (VIE).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 6
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=108788376&loc=d3e5747-111685

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 810
-SubTopic 10
-Section 50
-Paragraph 4
-Subparagraph b
-URI http://asc.fasb.org/extlink&oid=108788376&loc=d3e5728-111685

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