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Goodwill And Other Intangible Assets (Schedule Of Goodwill Allocated By Operating Segments) (Details) (USD $)
In Thousands, unless otherwise specified
Dec. 31, 2014
Dec. 31, 2013
Goodwill [Line Items]    
Goodwill $ 138,921us-gaap_Goodwill $ 138,921us-gaap_Goodwill
Consumer Segment [Member]    
Goodwill [Line Items]    
Goodwill 70,721us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= cbsh_ConsumerSegmentMember		 70,721us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= cbsh_ConsumerSegmentMember
Commercial Segment [Member]    
Goodwill [Line Items]    
Goodwill 67,454us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= cbsh_CommercialSegmentMember		 67,454us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= cbsh_CommercialSegmentMember
Wealth Segment [Member]    
Goodwill [Line Items]    
Goodwill $ 746us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= cbsh_WealthSegmentMember		 $ 746us-gaap_Goodwill
/ us-gaap_StatementBusinessSegmentsAxis
= cbsh_WealthSegmentMember