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Derivative Instruments Schedule of Swaptions (Details) (Interest Rate Swaption [Member], USD $) In Thousands, unless otherwise specified	9 Months Ended
	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