Counterparty Risk (% Of Total Collateral On Reverse Repurchase Agreements) (Details)	Jun. 30, 2018
Royal Bank of Canada [Member]
Concentration Risk [Line Items]
Percentage of Total Collateral On Reverse Repurchase Agreements	15.00%

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.

Name:	us-gaap_ConcentrationRiskLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration