Parent Company Only Financial Statements - Schedule Of Statement of Income (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating income
Total interest income	$ 34,437	$ 31,973	$ 29,034	$ 28,580	$ 28,394	$ 26,927	$ 25,781	$ 25,355	$ 124,024	$ 106,457	$ 79,014
Operating expense
Total interest expense	10,326	10,150	9,779	8,893	8,651	7,935	7,742	7,338	39,148	31,666	26,367
Income (loss) before income tax benefit and increase in equity in undistributed earnings of subsidiaries	7,689	4,792	4,408	4,271	5,880	5,164	6,344	4,497	21,160	21,885	14,341
Income tax benefit	5,867	5,673	4,198	4,013	(443)	3,130	2,952	1,926	19,751	7,565	5,407
Net income	13,556	10,465	8,606	8,284	5,437	8,294	9,296	6,423	40,911	29,450	19,748
Preferred stock dividends and discount accretion											(580)
Income available to common shareholders	13,461	10,403	8,511	8,189	4,967	8,051	9,202	6,210	40,564	28,430	18,068
First NBC Bank Holding Company [Member]
Operating income
Interest income
Dividend from bank subsidary									2,000
Total interest income									2,000
Operating expense
Interest expense									424	11	14
Other expense									856	431	188
Total interest expense									1,280	442	202
Income (loss) before income tax benefit and increase in equity in undistributed earnings of subsidiaries									720	(442)	(202)
Income tax benefit									(448)	(155)	(71)
Income (loss) before equity in undistributed earnings of subsidiaries									1,168	(287)	(131)
Equity in undistributed earnings of subsidiaries									39,743	29,227	19,571
Net income									40,911	28,940	19,440
Preferred stock dividends and discount accretion									(347)	(510)	(1,372)
Income available to common shareholders									$ 40,564	$ 28,430	$ 18,068