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Stock Option Plans (Narrative) (Details) (USD $)
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Jan. 01, 2001
Jan. 02, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Proceeds from stock options exercised $ 932,000us-gaap_ProceedsFromStockOptionsExercised $ 304,000us-gaap_ProceedsFromStockOptionsExercised $ 0us-gaap_ProceedsFromStockOptionsExercised    
Stock Options [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Total compensation cost not yet recognized 1,300,000us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognized
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
       
Total compensation cost not yet recognized, period for recognition, weighted average 2 years 3 months 18 days        
Intrinsic value of options outstanding and exercisable 5,900,000us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardOptionsExercisableIntrinsicValue1
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
       
Stock options exercisable, intrinsic value 716,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
183,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
   
Stock options outstanding, intrinsic value $ 0us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingIntrinsicValue
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
       
Stock options exercised, paid with stock 6,185metr_ShareBasedCompensationStockOptionsExercisedPaidWithStock
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
       
Stock options exercisable, weighted average remaining contractual life 4 years        
2006 Employee Stock Option Plan [Member] | Stock Options [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of shares authorized under stock option plan 1,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= metr_A2006EmployeeStockOptionPlanMember
       
Requisite service period under stock option plan 1 year        
Award vesting period under stock option plan 4 years        
Period from grant date to expiration under stock option plan 10 years        
2006 Employee Stock Option Plan [Member] | Qualified Incentive Stock Options [Member] | Minimum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Exercise price of stock options, percent of fair market value 100.00%metr_ShareBasedCompensationArrangementByShareBasedPaymentAwardExercisePriceOfStockOptionsPercent
/ us-gaap_AwardTypeAxis
= metr_QualifiedIncentiveStockOptionsMember
/ us-gaap_PlanNameAxis
= metr_A2006EmployeeStockOptionPlanMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember
       
2001 Directors' Stock Option Plan [Member] | Stock Options [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of shares authorized under stock option plan       343,100us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= metr_A2001DirectorsStockOptionPlanMember
 
2011 Directors' Stock Option Plan [Member] | Stock Options [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of shares authorized under stock option plan         200,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= metr_A2011DirectorsStockOptionPlanMember
2011 Directors' Stock Option Plan [Member] | Stock Options [Member] | Minimum [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Exercise price of stock options, percent of fair market value 100.00%metr_ShareBasedCompensationArrangementByShareBasedPaymentAwardExercisePriceOfStockOptionsPercent
/ us-gaap_AwardTypeAxis
= us-gaap_EmployeeStockOptionMember
/ us-gaap_PlanNameAxis
= metr_A2011DirectorsStockOptionPlanMember
/ us-gaap_RangeAxis
= us-gaap_MinimumMember