Note 7 - Segment Reporting - Reconciliation of Reportable Segment Revenue, Expenses and Profit (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Dec. 31, 2015
Operating Segments [Member] | Retail and Commercial Banking [Member]          
Interest income $ 16,251 $ 10,670 $ 47,681 $ 30,236  
Interest expense 1,898 1,158 5,174 3,191  
Net interest income 14,353 9,512 42,507 27,045  
Provision for loan and lease losses 289 310 2,118 738  
Noninterest income 1,791 545 4,734 1,469  
Noninterest expense 9,590 7,083 28,246 20,872  
Earnings before income taxes 6,265 2,664 16,877 6,904  
Income tax expense 2,187 967 5,706 2,452  
Noncontrolling interest  
Net earnings atributable to National Commerce Corporation 4,078 1,697 11,171 4,452  
Total assets 1,741,047 1,312,449 1,741,047 1,312,449  
Operating Segments [Member] | Mortgage Division [Member]          
Interest income [1] 145 104 411 301  
Interest expense [1] 61 33 165 98  
Net interest income [1] 84 71 246 203  
Provision for loan and lease losses [1]  
Noninterest income [1] 2,179 1,782 5,673 4,799  
Noninterest expense [1] 1,709 1,507 4,758 4,001  
Earnings before income taxes [1] 554 346 1,161 1,001  
Income tax expense [1] 211 131 441 380  
Noncontrolling interest [1]  
Net earnings atributable to National Commerce Corporation [1] 343 215 720 621  
Total assets [1] 7,810 7,926 7,810 7,926  
Operating Segments [Member] | Receivables Factoring [Member]          
Interest income 2,916 3,170 8,885 9,331  
Interest expense 476 494 1,446 1,511  
Net interest income 2,440 2,676 7,439 7,820  
Provision for loan and lease losses 84 (109) 689 (256)  
Noninterest income 32 26 77 55  
Noninterest expense 1,333 1,305 3,935 3,928  
Earnings before income taxes 1,055 1,506 2,892 4,203  
Income tax expense 241 355 647 977  
Noncontrolling interest (422) (573) (1,190) (1,632)  
Net earnings atributable to National Commerce Corporation 392 578 1,055 1,594  
Total assets 92,822 96,967 92,822 96,967  
Intersegment Eliminations [Member]          
Interest income [2] (476) (494) (1,446) (1,511)  
Interest expense [2] (476) (494) (1,446) (1,511)  
Net interest income [2]  
Provision for loan and lease losses [2]  
Noninterest income [2]  
Noninterest expense [2]  
Earnings before income taxes [2]  
Income tax expense [2]  
Noncontrolling interest [2]  
Net earnings atributable to National Commerce Corporation [2]  
Total assets [2] (62,401) (66,561) (62,401) (66,561)  
Interest income 18,836 13,450 55,531 38,357  
Interest expense 1,959 1,191 5,339 3,289  
Net interest income 16,877 12,259 50,192 35,068  
Provision for loan and lease losses 373 201 2,807 482  
Noninterest income 4,002 2,353 10,484 6,323  
Noninterest expense 12,632 9,895 36,939 28,801  
Earnings before income taxes 7,874 4,516 20,930 12,108  
Income tax expense 2,639 1,453 6,794 3,809  
Noncontrolling interest (422) (573) (1,190) (1,632)  
Net earnings atributable to National Commerce Corporation 4,813 2,490 12,946 6,667  
Total assets $ 1,779,278 $ 1,350,781 $ 1,779,278 $ 1,350,781 $ 1,763,369
[1] Noninterest income for the mortgage division segment includes intercompany income allocation.
[2] Entry to remove intercompany interest allocated to the receivables factoring segment. For segment reporting purposes, we allocate funding costs to the receivables factoring segment at the federal funds rate plus 2.50%.