Accumulated Other Comprehensive Income (Schedule Of Accumulated Other Comprehensive Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2012	Mar. 31, 2011	Dec. 31, 2011	Dec. 31, 2010
Accumulated Other Comprehensive Income [Abstract]
Unrealized Gains (Losses) on Securities, OTTI, Balance	$ (961)	$ (3,455)	$ (4,321)	$ (7,469)
Unrealized Gains (Losses) on Securities, OTTI, Current period other comprehensive income (loss)	3,360	4,014
Unrealized Gains (Losses) on Securities, Other, Balance	139,843	81,224	136,137	87,784
Unrealized Gains (Losses) on Securities, Other, Current period other comprehensive income (loss)	3,706	(6,560)
Pension Loss, Balance	(20,826)	(16,635)	(21,278)	(16,970)
Pension Loss, Current period other comprehensive income	452	335
Total Accumulated Other Comprehensive Income, Balance	118,056	61,134	110,538	63,345
Comprehensive income attributable to Commerce Bancshares, Inc	$ 7,518	$ (2,211)

The total of net gain (loss), prior service cost (credit), and transition assets (obligations), as well as minimum pension liability if still remaining, included in accumulated other comprehensive income associated with a defined benefit pension or other postretirement plan(s) because they have yet to be recognized as components of net periodic benefit cost.

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+ Details

- Definition

Accumulated change in equity from transactions and other events and circumstances from non-owner sources, net of tax effect, at period end. Excludes Net Income (Loss), and accumulated changes in equity from transactions resulting from investments by owners and distributions to owners. Includes foreign currency translation items, certain pension adjustments, unrealized gains and losses on certain investments in debt and equity securities, other than temporary impairment (OTTI) losses related to factors other than credit losses on available-for-sale and held-to-maturity debt securities that an entity does not intend to sell and it is not more likely than not that the entity will be required to sell before recovery of the amortized cost basis, as well as changes in the fair value of derivatives related to the effective portion of a designated cash flow hedge.

+ References

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 31

-Article 5

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-Name Accounting Principles Board Opinion (APB)

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+ Details

- Definition

The change in equity [net assets] of a business enterprise during a period from transactions and other events and circumstances from non-owner sources which are attributable to the reporting entity. It includes all changes in equity during a period except those resulting from investments by owners and distributions to owners, but excludes any and all transactions which are directly or indirectly attributable to that ownership interest in subsidiary equity which is not attributable to the parent.

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-Name Accounting Standards Codification

-Glossary Comprehensive Income

-URI http://asc.fasb.org/extlink&oid=6508144

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-Name Accounting Standards Codification

-Glossary Net Income

-URI http://asc.fasb.org/extlink&oid=6518256

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-Glossary Other Comprehensive Income

-URI http://asc.fasb.org/extlink&oid=6519514

+ Details