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This element represent book value of marketable securities.

No definition available.

Name:	sona_MarketableSecuritiesBookValue
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- References

No definition available.

Name:	sona_OtherThanTemporarilyImpairedAbstract
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Data Type:	xbrli:stringItemType
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This element represent book value of other than temporary impairment losses.

No definition available.

Name:	sona_OtherThanTemporaryImpairmentLossesBookValue
Namespace Prefix:	sona_
Data Type:	xbrli:monetaryItemType
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This element represent fair value of other than temporary impairment.

No definition available.

Name:	sona_OtherThanTemporaryImpairmentLossesFairValue
Namespace Prefix:	sona_
Data Type:	xbrli:monetaryItemType
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This element represent par value of other than temporarily impaired.

No definition available.

Name:	sona_OtherThanTemporaryImpairmentLossesParValue
Namespace Prefix:	sona_
Data Type:	xbrli:monetaryItemType
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Represents percentage of current defaults and deferrals to total collateral.

No definition available.

Name:	sona_PercentageOfCurrentDefaultsAndDeferralsToTotalCollateral
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Represents percentage of other than temporarily impaired current defaults and deferrals to total collateral.

No definition available.

Name:	sona_PercentageOfOtherThanTemporarilyImpairedCurrentDefaultsAndDeferralsToTotalCollateral
Namespace Prefix:	sona_
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This element represent book value of securities.

No definition available.

Name:	sona_SecuritiesBookValue
Namespace Prefix:	sona_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

This element represent fair value of securities.

No definition available.

Name:	sona_SecuritiesFairValue
Namespace Prefix:	sona_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

This element represent par value of securities.

No definition available.

Name:	sona_SecuritiesParValue
Namespace Prefix:	sona_
Data Type:	xbrli:monetaryItemType
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- References

No definition available.

Name:	sona_SecurityAbstract
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Period Type:	duration

Amount of investment in debt security measured at amortized cost (held-to-maturity) and investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

No definition available.

Name:	us-gaap_DebtSecuritiesAvailableForSaleAndHeldToMaturity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Amount of investment in marketable security.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03.4)
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

Name:	us-gaap_MarketableSecurities
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Data Type:	xbrli:monetaryItemType
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This item represents an increase to the cumulative amount of credit losses recognized in earnings for an other than temporary impairment (OTTI) of a debt security held for which no such other than temporary impairment (OTTI) was previously recognized.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 8B
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118939692&loc=SL6284393-111563

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Data Type:	xbrli:monetaryItemType
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Name:	us-gaap_FinancialInstrumentAxis=us-gaap_TrustPreferredSecuritiesSubjectToMandatoryRedemptionMember
Namespace Prefix:
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Name:	sona_SecurityAxis=sona_AlescoViiOneBSeniorMember
Namespace Prefix:
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Name:	srt_CreditRatingMoodysAxis=srt_MoodysAa1RatingMember
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Name:	srt_CreditRatingFitchAxis=srt_FitchAARatingMember
Namespace Prefix:
Data Type:	na
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Name:	sona_SecurityAxis=sona_TprefFundingIiMezzanineMember
Namespace Prefix:
Data Type:	na
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Name:	srt_CreditRatingMoodysAxis=srt_MoodysCaa3RatingMember
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Data Type:	na
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