The increase (decrease) in the allowance for credit losses related to financing receivables.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 11B
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=66008989&loc=SL6953423-111524

Name:	us-gaap_FinancingReceivableAllowanceForCreditLossesPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

Investments - Valuation Reserves for Commercial Mortgage Loans (Details) - USD ($)	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016
Mortgage Loans on Real Estate [Member]
Financing Receivable, Allowance for Credit Losses [Line Items]
Financing Receivable, Allowance For Credit Losses, Period Increase (Decrease)