Parent Company Only Financial Statements - Schedule Of Statement of Cash Flow (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating activities
Net income	$ 40,911	$ 28,940	$ 19,440
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Deferred tax benefit	(19,937)	(7,565)	(5,407)
Stock compensation	2,124	1,102	715
Changes in operating assets and liabilities:
Change in other assets	(5,168)	1,540	(6,854)
Change in other liabilities	15,125	(2,758)	7,224
Net cash provided by (used in) operating activities	89,463	1,198	28,678
Investing activities
Net cash used in investing activities	(665,076)	(454,155)	(343,559)
Financing activities
Repayment of borrowings	(41,910)	(1,625)	(21,220)
Repayment of preferred stock		(1,644)	(18,685)
Proceeds from sale of preferred stock, net of offering costs			58,518
Proceeds from sale of common stock, net of offering costs	104,332	1,420	30,430
Dividends paid	(347)	(510)	(792)
Net cash provided by financing activities	571,243	421,598	352,968
Net change in cash, due from banks, and short-term investments	(4,370)	(31,359)	38,087
Cash, due from banks, and short-term investments at beginning of period	36,012	67,371	29,284
Cash, due from banks, and short-term investments at end of period	31,642	36,012	67,371
First NBC Bank Holding Company [Member]
Operating activities
Net income	40,911	28,940	19,440
Adjustments to reconcile net income to net cash (used in) provided by operating activities:
Net income of subsidiaries	(39,743)	(29,227)	(19,571)
Deferred tax benefit	(448)	(155)	(71)
Stock compensation	1,155	97	715
Changes in operating assets and liabilities:
Change in other assets	1,481	(1,989)	(762)
Change in other liabilities	50		3
Net cash provided by (used in) operating activities	3,406	(2,334)	(246)
Investing activities
Capital contributed to subsidiary, net	(67,000)	(16,600)	(67,508)
Net cash used in investing activities	(67,000)	(16,600)	(67,508)
Financing activities
Proceeds from long-term borrowings		20,000
Repayment of borrowings	(20,110)	(110)	(110)
Repayment of preferred stock			(18,685)
Proceeds from sale of preferred stock, net of offering costs			58,518
Proceeds from sale of common stock, net of offering costs	104,332	1,420	30,430
Dividends paid	(347)	(510)	(792)
Net cash provided by financing activities	83,875	20,800	69,361
Net change in cash, due from banks, and short-term investments	20,281	1,866	1,607
Cash, due from banks, and short-term investments at beginning of period	3,709	1,843	236
Cash, due from banks, and short-term investments at end of period	$ 23,990	$ 3,709	$ 1,843