Note 20 - Stockholders' Equity - Company's Significant Subsidiaries (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Simmons First National Corporation [Member]
Capital	$ 912,948	$ 843,227
Capital to Risk Weighted Assets	15.10%	16.70%
Capital Required for Capital Adequacy	$ 483,681	$ 403,941
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	8.00%
Tier One Risk Based Capital	$ 872,707	$ 808,159
Tier One Risk Based Capital to Risk Weighted Assets	14.50%	16.00%
Tier One Risk Based Capital Required for Capital Adequacy	$ 361,120	$ 303,060
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	6.00%	6.00%
Common Equity Tier 1 Capital	$ 812,310	$ 716,737
Common Equity Tier 1 Capital to Average Assets	13.50%	14.20%
Common Equity Tier 1 Capital Required for Capital Adequacy	$ 270,770	$ 227,135
Common Equity Tier 1 Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Tier One Leverage Capital	$ 872,707	$ 808,159
Tier One Leverage Capital to Average Assets	11.00%	11.20%
Tier One Leverage Capital Required for Capital Adequacy	$ 317,348	$ 288,628
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
Simmons First National Bank [Member]
Capital	$ 830,921	$ 734,170
Capital to Risk Weighted Assets	13.80%	14.60%
Capital Required for Capital Adequacy	$ 481,693	$ 402,285
Capital Required for Capital Adequacy to Risk Weighted Assets	8.00%	8.00%
Capital Required to be Well Capitalized	$ 602,117	$ 502,856
Capital Required to be Well Capitalized to Risk Weighted Assets	10.00%	10.00%
Tier One Risk Based Capital	$ 790,673	$ 699,102
Tier One Risk Based Capital to Risk Weighted Assets	13.20%	13.90%
Tier One Risk Based Capital Required for Capital Adequacy	$ 359,397	$ 301,771
Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	6.00%	6.00%
Tier One Risk Based Capital Required to be Well Capitalized	$ 479,196	$ 402,361
Tier One Risk Based Capital Required to be Well Capitalized to Risk Weighted Assets	8.00%	8.00%
Common Equity Tier 1 Capital	$ 790,673	$ 699,102
Common Equity Tier 1 Capital to Average Assets	13.20%	13.90%
Common Equity Tier 1 Capital Required for Capital Adequacy	$ 269,548	$ 226,328
Common Equity Tier 1 Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%	4.50%
Common Equity Tier 1 Capital Required to Be Well Capitalized	$ 389,347	$ 326,918
Common Equity Tier 1 Capital Required to Be Well Capitalized to Average Assets	6.50%	6.50%
Tier One Leverage Capital	$ 790,673	$ 699,102
Tier One Leverage Capital to Average Assets	10.00%	9.70%
Tier One Leverage Capital Required for Capital Adequacy	$ 316,269	$ 288,289
Tier One Leverage Capital Required for Capital Adequacy to Average Assets	4.00%	4.00%
us-gaap_TierOneLeverageCapitalRequiredToBeWellCapitalized	$ 395,337	$ 360,362
Tier One Leverage Capital Required to be Well Capitalized to Average Assets	5.00%	5.00%

The amount of common equity tier 1 capital as defined in the regulations.

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The minimum Total risk based capital ratio (total capital divided by risk weighted assets) required for capital adequacy purposes under the regulatory framework for prompt corrective action.

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The minimum amount of Tier 1 Leverage Capital for capital adequacy purposes divided by average assets as defined in the regulations.

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Tier 1 Leverage Capital divided by average assets as defined in the regulations.

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Tier 1 Risk Based Capital as defined in the regulations.

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Tier 1 capital divided by risk weighted assets as defined by regulations.

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