Condensed Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	County Commerce Bank [Member]	Valley Commerce Bancorp [Member]	Common Stock [Member]	Common Stock [Member] County Commerce Bank [Member]	Common Stock [Member] Valley Commerce Bancorp [Member]	Retained Earnings [Member]	Retained Earnings [Member] County Commerce Bank [Member]	Retained Earnings [Member] Valley Commerce Bancorp [Member]	Accumulated Other Comprehensive Income [Member]	Accumulated Other Comprehensive Income [Member] County Commerce Bank [Member]	Accumulated Other Comprehensive Income [Member] Valley Commerce Bancorp [Member]
Beginning balance at Dec. 31, 2015	$ 923,399			$ 502,571			$ 399,919			$ 20,909
Beginning balance, shares at Dec. 31, 2015				106,385
Repurchase of common stock	(496)			$ (496)			0			0
Repurchase of common stock, shares				(66)
Issuance of common stock for acquisition		$ 21,642			$ 21,642			$ 0			$ 0
Issuance of common stock for acquisition, shares					1,394
Exercise of stock options	3,174			$ 3,174			0			0
Exercise of stock options, shares				274
Tax benefit from exercise of stock options	236			$ 236			0			0
Shares issued pursuant to stock-based compensation plan	2,154			$ 2,154			0			0
Shares issued pursuant to stock-based compensation plan, shares				110
Cash dividends declared on common stock	(38,853)			$ 0			(38,853)			0
Net earnings	74,353			0			74,353			0
Other comprehensive income	17,694			0			0			17,694
Ending balance at Sep. 30, 2016	1,003,303			$ 529,281			435,419			38,603
Ending balance, shares at Sep. 30, 2016				108,097
Beginning balance at Dec. 31, 2016	990,862			$ 531,192			449,499			10,171
Beginning balance, shares at Dec. 31, 2016				108,252
Cumulative adjustment upon adoption of ASU 2016-09	50			$ 116			(66)			0
Repurchase of common stock	(997)			$ (997)			0			0
Repurchase of common stock, shares				(45)
Issuance of common stock for acquisition			$ 37,637			$ 37,637			$ 0			$ 0
Issuance of common stock for acquisition, shares						1,634
Exercise of stock options	2,537			$ 2,537			0			0
Exercise of stock options, shares				270
Shares issued pursuant to stock-based compensation plan	2,200			$ 2,200			0			0
Shares issued pursuant to stock-based compensation plan, shares				46
Cash dividends declared on common stock	(44,058)			$ 0			(44,058)			0
Net earnings	86,560			0			86,560			0
Other comprehensive income	1,673			0			0			1,673
Ending balance at Sep. 30, 2017	$ 1,076,464			$ 572,685			$ 491,935			$ 11,844
Ending balance, shares at Sep. 30, 2017				110,157