Parent Company Condensed Financial Statements (Condensed Balance Sheets) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Available for sale securities	$ 9,777,004	$ 9,523,560
Non-marketable securities	112,786	106,875
Other assets	534,625	380,823
Total assets	24,604,962	23,994,280
Other liabilities	191,321	217,680
Total liabilities	22,237,544	21,660,034
Stockholders’ equity	2,361,990	2,330,193
Total liabilities and equity	24,604,962	23,994,280
Commerce Bancshares, Inc. (Parent) [Member]
Investment in consolidated subsidiary, Banks	2,147,284	2,069,369
Investment in consolidated subsidiaries, Non-banks	50,223	45,600
Cash	53	56
Securities purchased under agreements to resell	104,440	161,650
Available for sale securities	52,076	52,118
Non-marketable securities	1,787	1,787
Advances to subsidiaries, net of borrowings	18,560	19,731
Income tax benefits	8,444	3,848
Other assets	17,246	16,551
Total assets	2,400,113	2,370,710
Pension obligation	18,237	20,653
Other liabilities	19,886	19,864
Total liabilities	38,123	40,517
Stockholders’ equity	2,361,990	2,330,193
Total liabilities and equity	$ 2,400,113	$ 2,370,710