Fair Value of Financial Instruments (Carrying Value of Commercial Mortgage Loans and Additional Information) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
Mar. 31, 2019	Dec. 31, 2018
Financing Receivable, Recorded Investment [Line Items]
Total amortized cost	$ 34,271	$ 25,828
Allowance allowance	(62)	(46)
Carrying Value	34,209	25,782
Total mortgage loans \| Mortgage Loans by Region
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 34,271	$ 25,828
Percent of Total	100.00%	100.00%
Total mortgage loans \| Mortgage Loans by Region \| East North Central
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 3,245	$ 3,244
Percent of Total	9.50%	12.60%
Total mortgage loans \| Mortgage Loans by Region \| Southern Atlantic
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 6,652	$ 6,652
Percent of Total	19.40%	25.80%
Total mortgage loans \| Mortgage Loans by Region \| East South Central
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 4,937	$ 4,975
Percent of Total	14.40%	19.30%
Total mortgage loans \| Mortgage Loans by Region \| New England
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 6,588	$ 6,588
Percent of Total	19.20%	25.40%
Total mortgage loans \| Mortgage Loans by Region \| Middle Atlantic
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 12,849	$ 4,369
Percent of Total	37.50%	16.90%
Total mortgage loans \| Property Type Concentration Risk
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 34,271	$ 25,828
Percent of Total	100.00%	100.00%
Total mortgage loans \| Property Type Concentration Risk \| Multifamily
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 3,245	$ 3,244
Percent of Total	9.50%	12.60%
Total mortgage loans \| Property Type Concentration Risk \| Office
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 11,589	$ 11,627
Percent of Total	33.80%	45.00%
Total mortgage loans \| Property Type Concentration Risk \| Mixed use/Other
Financing Receivable, Recorded Investment [Line Items]
Carrying Value	$ 19,437	$ 10,957
Percent of Total	56.70%	42.40%
Less than 65%
Financing Receivable, Recorded Investment [Line Items]
Total amortized cost	$ 25,775	$ 25,828
65% to 75%
Financing Receivable, Recorded Investment [Line Items]
Total amortized cost	$ 8,496	$ 0

The reserve to cover probable credit losses related to specifically identified fixed maturity real estate loans as well as probable credit losses inherent in the remainder of that loan portfolio.

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No definition available.

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Amount before allowance of mortgage loans on existing land or building. Includes deferred interest and fees, undisbursed portion of loan balance, unamortized costs and premiums and discounts from face amounts. Excludes loans covered under loss sharing agreements.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio.

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