Parent Company Condensed Financial Statements (Condensed Statements Of Income) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Interest and dividends on investment securities	$ 189,415	$ 211,682	$ 219,348
Salaries and employee benefits	366,867	360,899	345,325
Data processing fees paid to affiliates	78,245	73,798	68,103
Other	72,603	70,226	64,497
Total expense	629,633	618,469	617,249
Income tax expense (benefit)	122,230	127,169	121,412
Net income	260,961	269,329	256,343
Commerce Bancshares, Inc. (Parent) [Member]
Dividends received from consolidated subsidiary banks	200,001	235,000	180,001
Dividends received from consolidated nonbank subsidiaries	390	0	115
Earnings of consolidated subsidiaries, net of dividends	62,815	34,467	74,260
Interest and dividends on investment securities	4,029	5,074	7,997
Management fees charged subsidiaries	20,701	23,658	19,318
Investment securities gains (losses)	1,294	346	0
Other	2,958	2,067	1,560
Total income	292,188	300,612	283,251
Salaries and employee benefits	20,433	24,188	21,572
Professional fees	3,538	1,950	1,826
Data processing fees paid to affiliates	2,775	2,664	3,351
Indemnification obligation	0	0	(4,432)
Other	10,236	7,582	5,975
Total expense	36,982	36,384	28,292
Income tax expense (benefit)	(5,755)	(5,101)	(1,384)
Net income	$ 260,961	$ 269,329	$ 256,343