Investment Portfolio, Number of Securities by Type

No definition available.

Name:	metr_InvestmentPortfolioNumberOfSecuritiesByType
Namespace Prefix:	metr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	metr_InvestmentSecuritiesLineItems
Namespace Prefix:	metr_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Investment Securities, Return on Principal, Percentage

+ References

No definition available.

+ Details

Name:	metr_InvestmentSecuritiesReturnOnPrincipalPercentage
Namespace Prefix:	metr_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of Securities Called at Par

+ References

No definition available.

+ Details

Name:	metr_NumberOfSecuritiesCalledAtPar
Namespace Prefix:	metr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of Securities Sold

+ References

No definition available.

+ Details

Name:	metr_NumberOfSecuritiesSold
Namespace Prefix:	metr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The net gain (loss) realized from the sale, exchange, redemption, or retirement of securities, not separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-04.13(h))

-URI http://asc.fasb.org/extlink&oid=6879574&loc=d3e536633-122882

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 13

-Subparagraph h

-Article 9

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 225

-Section S99

-Paragraph 1

-Subparagraph (SX 210.7-04.3)

-URI http://asc.fasb.org/extlink&oid=6879464&loc=d3e573970-122913

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 04

-Paragraph 3

-Article 7

+ Details

Name:	us-gaap_GainLossOnSaleOfSecuritiesNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Fair value of investments in debt securities classified as held-to-maturity.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (aa)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (f)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 50

-Paragraph 5

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=27724398&loc=d3e27232-111563

+ Details

Name:	us-gaap_HeldToMaturitySecuritiesFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Sum of the carrying amounts as of the date of the latest financial statement presented of securities which are owned but transferred to another party to serve as collateral to partially or fully secure a debt obligation, repurchase agreement or other current or potential obligation, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 860

-SubTopic 30

-Section 50

-Paragraph 1A

-Subparagraph (b)(1)(i)

-URI http://asc.fasb.org/extlink&oid=34720971&loc=SL6224234-111729

+ Details

Name:	us-gaap_PledgedFinancialInstrumentsNotSeparatelyReportedSecuritiesPledged
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The cash inflow associated with the aggregate amount received by the entity through sale or maturity of marketable securities (held-to-maturity or available-for-sale) during the period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 320

-SubTopic 10

-Section 45

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=6871852&loc=d3e26853-111562

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 12

-Subparagraph (a),(b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3179-108585

+ Details

Name:	us-gaap_ProceedsFromSaleAndMaturityOfMarketableSecurities
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_GainLossOnInvestmentsByCategoryAxis=us-gaap_AvailableforsaleSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_GainLossOnInvestmentsByCategoryAxis=us-gaap_HeldtomaturitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_InformationByCategoryOfDebtSecurityAxis=us-gaap_AvailableforsaleSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=metr_AmortizingSecuritiesReturnedAtLeast85OfPrincipalMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_MortgageBackedSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_MortgageBackedSecuritiesOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_MunicipalBondsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorTypesOfDebtAndEquitySecuritiesAxis=us-gaap_USGovernmentAgenciesDebtSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Securities (Narrative) (Details) (USD $)	3 Months Ended
Securities (Narrative) (Details) (USD $)	Mar. 31, 2015 security_type security	Mar. 31, 2014 security	Dec. 31, 2014
Investment Securities [Line Items]
Held-to-maturity Securities, Fair Value	$ 323,056,000		$ 319,923,000
Number of securities called	0metr_NumberOfSecuritiesCalledAtPar	0metr_NumberOfSecuritiesCalledAtPar
Net gains (losses) on sales/calls of securities	(28,000)us-gaap_GainLossOnSaleOfSecuritiesNet	11,000us-gaap_GainLossOnSaleOfSecuritiesNet
Number of securities, type	2
Securities pledged to secure public deposits and other	646,300,000
Available-for-sale Securities [Member]
Investment Securities [Line Items]
Number of securities sold	4
Proceeds from sale of securities	27,800,000
Mortgage Backed Securities, Other [Member]
Investment Securities [Line Items]
Number of securities, type	4
Collateralized mortgage obligations [Member]
Investment Securities [Line Items]
Number of securities, type	19
Government Agency Debentures [Member]
Investment Securities [Line Items]
Number of securities, type	10
Amortizing Securities, Returned At Least 85% of Principal [Member] \| Held-to-maturity Securities [Member]
Investment Securities [Line Items]
Number of securities sold	1	1
Held-to-maturity Securities, Fair Value	1,400,000	614,000
Net gains (losses) on sales/calls of securities		11,000
Investment securities, return on principal, percentage (at least)	85.00%	85.00%
Municipal Bonds [Member]
Investment Securities [Line Items]
Number of securities, type	3
Available-for-sale Securities [Member]
Investment Securities [Line Items]
Net gains (losses) on sales/calls of securities	166,000
Held-to-maturity Securities [Member]
Investment Securities [Line Items]
Net gains (losses) on sales/calls of securities	$ 138,000