Reinsurance - Reinsurance Recoverables and Financial Strength Ratings by Reinsurer (Parenthetical) (Details)	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Standard & Poor's, AA- Rating [Member] \| Munich Re Novation Agreement [Member]
Ceded Credit Risk [Line Items]
Percentage of risks and rewards of term life insurance policies in force	80.00%	80.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration