XML 104 R88.htm IDEA: XBRL DOCUMENT v3.20.4

Goodwill And Other Intangible Assets (Schedule Of Changes In Carrying Amount Of Goodwill And Net Other Intangible Assets) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Goodwill [Roll Forward]
Amortization	$ 2,400	$ 1,500	$ 1,300
Core Deposit Premium [Member]
Goodwill [Roll Forward]
Balance, beginning	1,785	2,316
Originations	0	0
Amortization	(427)	(531)
Impairment	0	0
Balance, ending	1,358	1,785	2,316
Mortgage Servicing Rights
Goodwill [Roll Forward]
Balance, beginning	7,749	6,478
Originations	2,296	2,603
Amortization	(2,020)	(1,005)
Impairment	(1,776)	(327)
Balance, ending	6,249	7,749	6,478
Goodwill [Member]
Goodwill [Roll Forward]
Balance, beginning	138,921	138,921
Originations	0	0
Amortization	0	0
Impairment	0	0
Balance, ending	138,921	138,921	138,921
Easement
Goodwill [Roll Forward]
Balance, beginning	0	0
Originations	3,600	0
Amortization	0	0
Impairment	0	0
Balance, ending	$ 3,600	$ 0	$ 0

X

- Definition

Carrying amount as of the balance sheet date, which is the cumulative amount paid, adjusted for any amortization recognized prior to adoption of FAS 142 and for any impairment charges, in excess of the fair value of net assets acquired in one or more business combination transactions and the sum of the carrying amounts of all intangible assets, net of accumulated amortization and impairment charges.

+ References

No definition available.

+ Details

Name:	cbsh_GoodwillAndIntangibleAssetsNet
Namespace Prefix:	cbsh_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

The amount of impairment loss or impairment reversal recognized in the period resulting from the write-down or write-up of the carrying amount of a finite-lived intangible asset to fair value.

+ References

No definition available.

+ Details

Name:	cbsh_ImpairmentAndImpairmentReversalsOfIntangibleAssetsFiniteLived
Namespace Prefix:	cbsh_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

X

- Definition

The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121586364&loc=d3e3602-108585

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16323-109275

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6388964&loc=d3e16225-109274

+ Details

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

X

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

X

- Definition

The value of new servicing assets, subsequently measured at fair value, acquired or created during the current period through purchases or from transfers of financial assets.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 3
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122625-111746

+ Details

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

X

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CoreDepositsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_ServicingContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_GoodwillMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_UnclassifiedIndefinitelivedIntangibleAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: