Consolidated Statements Of Comprehensive Income (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Statement of Income and Comprehensive Income [Abstract]
Net income	$ 71,236	$ 69,617	$ 138,050	$ 130,567
Available for sale debt securities for which a portion of an other-than-temporary impairment (OTTI) has been recorded in earnings:
Unrealized holding gains (losses) subsequent to initial OTTI recognition	866	(812)	6,286	5,663
Income tax (expense) benefit	(329)	309	(2,389)	(2,152)
Net unrealized gains (losses) on OTTI securities	537	(503)	3,897	3,511
Other available for sale investment securities:
Unrealized holding gains	28,526	35,540	34,845	25,135
Reclassification adjustment for gains included in net income	0	(1)	(342)	(177)
Net unrealized gains on securities	28,526	35,539	34,503	24,958
Income tax expense	(10,840)	(13,505)	(13,111)	(9,484)
Net unrealized gains on other securities	17,686	22,034	21,392	15,474
Prepaid pension cost:
Amortization of accumulated pension loss	730	540	1,460	1,080
Income tax expense	(277)	(205)	(555)	(410)
Pension loss amortization	453	335	905	670
Other comprehensive income	18,676	21,866	26,194	19,655
Comprehensive income	89,912	91,483	164,244	150,222
Non-controlling interest expense	(503)	(583)	(1,518)	(1,080)
Comprehensive income attributable to Commerce Bancshares, Inc	$ 89,409	$ 90,900	$ 162,726	$ 149,142