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Derivative Instruments Schedule of Swaptions (Details) (Interest Rate Swaption [Member], USD $) In Thousands, unless otherwise specified | 9 Months Ended
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Sep. 30, 2013
Interest Rate Swaption [Member] |
Derivative [Line Items] |
Fixed Pay Rate on Derivatives | 3.31%
Maturity term of asset underlying derivative contract | 10 years
Derivative notional | $ 22,000
Derivative, Remaining Maturity | 12 months

X
- Definition Derivative notional amount. + References No definition available. + Details
Name: | earn_Derivativenotional
Namespace Prefix: | earn_
Data Type: | xbrli:monetaryItemType
Balance Type: | na
Period Type: | instant

X
- Definition Fixed rate paid on a derivative contract. + References No definition available. + Details
Name: | earn_FixedPayRateonDerivatives
Namespace Prefix: | earn_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Term to maturity of the reference asset underlying the derivative contract. + References No definition available. + Details
Name: | earn_Maturitytermofassetunderlyingderivativecontract
Namespace Prefix: | earn_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | instant

X
- Details
Name: | us-gaap_DerivativeLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period remaining until the derivative contract matures, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_DerivativeRemainingMaturity1
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration