Actual Capital Amounts as well as Required and Well-Capitalized Common Equity Tier One, Tier One, Total and Tier One Leverage Ratios (Detail) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital, Actual Ratio	11.80%
Tier 1 Capital For Capital Adequacy Purposes, Ratio	6.00%		4.00%
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	8.00%
Total Capital, Actual Ratio	12.87%
Total Capital For Capital Adequacy Purposes, Ratio	8.00%		8.00%
Total Capital To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%
Tier 1 Leverage, Actual Ratio	9.09%
Tier 1 Leverage for Capital Adequacy Purposes, Ratio	4.00%		4.00%
Tier 1 Leverage To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%
Common Equity Tier One Capital [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital, Actual Ratio	11.80%
Tier 1 Capital For Capital Adequacy Purposes, Ratio	4.50%
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	6.50%
Total Capital, Actual Ratio	4.50%
UMB Financial Corporation [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital, Actual Amount	$ 1,789,581	$ 1,681,222
Tier 1 Capital, Actual Ratio	11.80%	11.86%
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 909,903	$ 850,810
Tier 1 Capital For Capital Adequacy Purposes, Ratio	6.00%	6.00%
Total Capital, Actual Amount	$ 1,951,078	$ 1,814,705
Total Capital, Actual Ratio	12.87%	12.80%
Total Capital For Capital Adequacy Purposes, Amount	$ 1,213,205	$ 1,134,413
Total Capital For Capital Adequacy Purposes, Ratio	8.00%	8.00%
Tier 1 Leverage, Actual Amount	$ 1,789,581	$ 1,681,222
Tier 1 Leverage, Actual Ratio	9.09%	9.08%
Tier 1 Leverage For Capital Adequacy Purposes, Amount	$ 787,604	$ 740,918
Tier 1 Leverage for Capital Adequacy Purposes, Ratio	4.00%	4.00%
UMB Financial Corporation [Member] | Common Equity Tier One Capital [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital, Actual Amount	$ 1,789,581	$ 1,664,815
Tier 1 Capital, Actual Ratio	11.80%	11.74%
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 682,428	$ 638,108
Tier 1 Capital For Capital Adequacy Purposes, Ratio	4.50%	4.50%
UMB Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital, Actual Amount	$ 1,613,024	$ 1,491,833
Tier 1 Capital, Actual Ratio	10.73%	10.63%
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 901,809	$ 842,353
Tier 1 Capital For Capital Adequacy Purposes, Ratio	6.00%	6.00%
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 1,202,412	$ 1,123,138
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	8.00%	8.00%
Total Capital, Actual Amount	$ 1,707,265	$ 1,575,697
Total Capital, Actual Ratio	11.36%	11.22%
Total Capital For Capital Adequacy Purposes, Amount	$ 1,202,412	$ 1,123,138
Total Capital For Capital Adequacy Purposes, Ratio	8.00%	8.00%
Total Capital To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 1,503,016	$ 1,403,922
Total Capital To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	10.00%	10.00%
Tier 1 Leverage, Actual Amount	$ 1,613,024	$ 1,491,833
Tier 1 Leverage, Actual Ratio	8.24%	8.13%
Tier 1 Leverage For Capital Adequacy Purposes, Amount	$ 782,638	$ 734,229
Tier 1 Leverage for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Tier 1 Leverage To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 978,297	$ 917,786
Tier 1 Leverage To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	5.00%	5.00%
UMB Bank [Member] | Common Equity Tier One Capital [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Tier 1 Capital, Actual Amount	$ 1,613,024	$ 1,491,833
Tier 1 Capital, Actual Ratio	10.73%	10.63%
Tier 1 Capital For Capital Adequacy Purposes, Amount	$ 676,357	$ 631,765
Tier 1 Capital For Capital Adequacy Purposes, Ratio	4.50%	4.50%
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Action Provisions, Amount	$ 976,960	$ 912,549
Tier 1 Capital To Be Well Capitalized Under Prompt Corrective Action Provisions, Ratio	6.50%	6.50%