Loans Receivable and Allowance for Loan Losses (Schedule of Impaired Loan Receivables, Average) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Loans With No Related Allowance:
Average Recorded Investment	$ 36,655	$ 38,810
Interest Income Recognized	130	135
Loans With An Allowance Recorded:
Average Recorded Investment	10,359	11,964
Interest Income Recognized	0	0
Total Impaired Loans:
Average Recorded Investment	47,014	50,774
Interest Income Recognized	130	135
Commercial and industrial [Member]
Loans With No Related Allowance:
Average Recorded Investment	8,849	7,890
Interest Income Recognized	70	40
Loans With An Allowance Recorded:
Average Recorded Investment	8,572	3,246
Interest Income Recognized	0	0
Total Impaired Loans:
Average Recorded Investment	17,421	11,136
Interest Income Recognized	70	40
Commercial tax-exempt [Member]
Loans With No Related Allowance:
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Total Impaired Loans:
Average Recorded Investment	0	0
Interest Income Recognized	0	0
Owner occupied real estate [Member]
Loans With No Related Allowance:
Average Recorded Investment	5,459	4,786
Interest Income Recognized	0	10
Loans With An Allowance Recorded:
Average Recorded Investment	1,787	1,686
Interest Income Recognized	0	0
Total Impaired Loans:
Average Recorded Investment	7,246	6,472
Interest Income Recognized	0	10
Commercial construction and land development [Member]
Loans With No Related Allowance:
Average Recorded Investment	3,679	8,241
Interest Income Recognized	6	17
Loans With An Allowance Recorded:
Average Recorded Investment	0	3,477
Interest Income Recognized	0	0
Total Impaired Loans:
Average Recorded Investment	3,679	11,718
Interest Income Recognized	6	17
Commercial real estate [Member]
Loans With No Related Allowance:
Average Recorded Investment	10,662	10,770
Interest Income Recognized	39	48
Total Impaired Loans:
Average Recorded Investment	10,662	10,770
Interest Income Recognized	39	48
Residential [Member]
Loans With No Related Allowance:
Average Recorded Investment	5,669	4,488
Interest Income Recognized	8	13
Loans With An Allowance Recorded:
Average Recorded Investment	0	3,079
Interest Income Recognized	0	0
Total Impaired Loans:
Average Recorded Investment	5,669	7,567
Interest Income Recognized	8	13
Consumer [Member]
Loans With No Related Allowance:
Average Recorded Investment	2,337	2,635
Interest Income Recognized	7	7
Loans With An Allowance Recorded:
Average Recorded Investment	0	476
Interest Income Recognized	0	0
Total Impaired Loans:
Average Recorded Investment	2,337	3,111
Interest Income Recognized	$ 7	$ 7

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

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

- Definition

Average amount of investment of impaired financing receivables with related allowance for credit losses and without a related allowance for credit losses.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 15

-Subparagraph (c)(1)

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5212-111524

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 310

-SubTopic 10

-Section 50

-Paragraph 17

-URI http://asc.fasb.org/extlink&oid=35738203&loc=d3e5258-111524

+ Details

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

- Definition

Amount of interest income recognized that the financing receivables (with related allowance for credit losses and without a related allowance for credit losses) were impaired.

+ References

+ Details

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

- Definition

Amount of average investment of impaired financing receivables for which there is no related allowance for credit losses.

+ References

+ Details

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

- Definition

Amount of interest income, recognized on accrual basis, on financing receivables that are recognized as impaired, for which there is no related allowance for credit losses.

+ References

+ Details

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

- Definition

Amount of average investment of impaired financing receivables for which there is a related allowance for credit losses.

+ References

+ Details

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

- Definition

Amount of interest income, recognized on accrual basis, on financing receivables, for which there is a related allowance for credit losses and are recognized as impaired.

+ References

+ Details

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

- Details

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

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=metr_CommercialAndIndustrialMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=metr_CommercialConstructionAndLandDevelopmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=metr_CommercialTaxExemptMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=metr_OwnerOccupiedRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_CommercialRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ConsumerLoanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FinancingReceivableRecordedInvestmentByClassOfFinancingReceivableAxis=us-gaap_ResidentialPortfolioSegmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: