Consolidated Statements Of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
INTEREST INCOME
Interest and fees on loans	$ 625,083	$ 543,825	$ 489,956
Interest on loans held for sale	1,298	1,000	1,317
Interest on investment securities	240,187	214,689	207,184
Interest on federal funds sold and short-term securities purchased under agreements to resell	519	230	78
Interest on long-term securities purchased under agreements to resell	15,881	15,440	13,544
Interest on deposits with banks	6,233	2,223	973
Total interest income	889,201	777,407	713,052
INTEREST EXPENSE
Savings, interest checking and money market	27,803	17,309	14,366
Time open and C.D.’s of less than $100,000	3,215	2,645	2,809
Time open and C.D.’s of $100,000 and over	14,658	10,859	8,545
Interest on federal funds purchased and securities sold under agreements to repurchase	19,655	9,829	3,315
Interest on other borrowings	45	3,086	3,968
Total interest expense	65,376	43,728	33,003
Net interest income	823,825	733,679	680,049
Provision for loan losses	42,694	45,244	36,318
Net interest income after provision for loan losses	781,131	688,435	643,731
NON-INTEREST INCOME
Bank card transaction fees	171,576	155,100	154,043
Trust fees	147,964	135,159	121,795
Deposit account charges and other fees	94,517	90,060	86,394
Capital market fees	7,721	7,996	10,655
Consumer brokerage	15,807	14,630	13,784
Loan fees and sales	12,723	13,948	11,412
Other	51,033	44,370	48,473
Total non-interest income	501,341	461,263	446,556
INVESTMENT SECURITIES GAINS (LOSSES), NET
Investment securities gains (losses), net	(488)	25,051	(53)
NON-INTEREST EXPENSE
Salaries and employee benefits	468,194	448,321	427,310
Net occupancy	46,044	45,612	46,290
Equipment	18,125	18,568	19,141
Supplies and communication	20,637	22,790	24,135
Data processing and software	85,978	80,998	79,589
Marketing	20,548	16,325	16,032
Deposit insurance	11,546	13,986	13,327
Community Service	2,445	34,377	3,906
Other	64,304	63,366	59,499
Total non-interest expense	737,821	744,343	689,229
Income before income taxes	544,163	430,406	401,005
Less income taxes	105,949	110,506	124,151
Net income	438,214	319,900	276,854
Less non-controlling interest expense	4,672	517	1,463
NET INCOME ATTRIBUTABLE TO COMMERCE BANCSHARES, INC.	433,542	319,383	275,391
Preferred stock dividends	9,000	9,000	9,000
Net Income (Loss) Available to Common Stockholders, Basic	$ 424,542	$ 310,383	$ 266,391
Net income per common share - basic (in dollars per share)	$ 3.79	$ 2.77	$ 2.38
Net income per common share - diluted (in dollars per share)	$ 3.78	$ 2.76	$ 2.37