XML 44 R43.htm IDEA: XBRL DOCUMENT v2.4.1.9
Loans And Allowance For Loan Losses (Total Average Impaired Loans) (Details) (USD $)
In Thousands, unless otherwise specified
 3 Months Ended
Mar. 31, 2015
Mar. 31, 2014
Loans And Allowance For Loan Losses [Line Items]    
Non-accrual loans $ 37,539cbsh_FinancingReceivableAverageRecordedInvestmentNonaccrualStatus $ 47,867cbsh_FinancingReceivableAverageRecordedInvestmentNonaccrualStatus
Restructured loans (accruing) 41,666cbsh_FinancingReceivableModificationsAverageRecordedInvestment 59,824cbsh_FinancingReceivableModificationsAverageRecordedInvestment
Total 79,205us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment 107,691us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
Commercial Portfolio Segment [Member]    
Loans And Allowance For Loan Losses [Line Items]    
Non-accrual loans 31,281cbsh_FinancingReceivableAverageRecordedInvestmentNonaccrualStatus
/ cbsh_AverageImpairedLoansAxis
= us-gaap_CommercialPortfolioSegmentMember		 40,302cbsh_FinancingReceivableAverageRecordedInvestmentNonaccrualStatus
/ cbsh_AverageImpairedLoansAxis
= us-gaap_CommercialPortfolioSegmentMember
Restructured loans (accruing) 22,280cbsh_FinancingReceivableModificationsAverageRecordedInvestment
/ cbsh_AverageImpairedLoansAxis
= us-gaap_CommercialPortfolioSegmentMember		 38,393cbsh_FinancingReceivableModificationsAverageRecordedInvestment
/ cbsh_AverageImpairedLoansAxis
= us-gaap_CommercialPortfolioSegmentMember
Total 53,561us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ cbsh_AverageImpairedLoansAxis
= us-gaap_CommercialPortfolioSegmentMember		 78,695us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ cbsh_AverageImpairedLoansAxis
= us-gaap_CommercialPortfolioSegmentMember
Personal Banking Portfolio Segment [Member]    
Loans And Allowance For Loan Losses [Line Items]    
Non-accrual loans 6,258cbsh_FinancingReceivableAverageRecordedInvestmentNonaccrualStatus
/ cbsh_AverageImpairedLoansAxis
= cbsh_PersonalBankingPortfolioSegmentMember		 7,565cbsh_FinancingReceivableAverageRecordedInvestmentNonaccrualStatus
/ cbsh_AverageImpairedLoansAxis
= cbsh_PersonalBankingPortfolioSegmentMember
Restructured loans (accruing) 19,386cbsh_FinancingReceivableModificationsAverageRecordedInvestment
/ cbsh_AverageImpairedLoansAxis
= cbsh_PersonalBankingPortfolioSegmentMember		 21,431cbsh_FinancingReceivableModificationsAverageRecordedInvestment
/ cbsh_AverageImpairedLoansAxis
= cbsh_PersonalBankingPortfolioSegmentMember
Total $ 25,644us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ cbsh_AverageImpairedLoansAxis
= cbsh_PersonalBankingPortfolioSegmentMember		 $ 28,996us-gaap_ImpairedFinancingReceivableAverageRecordedInvestment
/ cbsh_AverageImpairedLoansAxis
= cbsh_PersonalBankingPortfolioSegmentMember