Consolidated Statements Of Comprehensive Income - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 114,069	$ 74,226	$ 327,454	$ 224,917
Other comprehensive income (loss)
Net unrealized gains (losses) on securities for which a portion of an other-than-temporary impairment has been recorded in earnings	53	286	(25)	457
Net unrealized gains (losses) on other securities	(32,232)	24,356	(125,442)	54,599
Pension loss amortization	393	349	1,180	1,030
Unrealized losses on cash flow hedge derivatives	(1,029)	0	(1,029)	0
Other comprehensive income (loss), net of tax	(32,815)	24,991	(125,316)	56,086
Comprehensive income	81,254	99,217	202,138	281,003
Non-controlling interest expense (income)	1,493	(338)	3,564	(111)
Comprehensive income attributable to Commerce Bancshares, Inc	$ 79,761	$ 99,555	$ 198,574	$ 281,114