Condensed Financial Information of Cadence Bancorporation (Parent Only) - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
CASH FLOWS FROM OPERATING ACTIVITIES
Net income	$ 32,326	$ 47,136	$ 47,974	$ 38,825	$ 14,691	$ 32,577	$ 28,968	$ 26,117	$ 166,261	$ 102,353	$ 65,774
Adjustments to reconcile net income to net cash provided by operations:
Deferred income tax expense									4,464	44,388	5,980
(Increase) decrease in other assets									(21,644)	4,079	(11,685)
Increase (decrease) in other liabilities									1,610	18,078	1,011
Net cash flows provided by operating activities									191,169	144,698	118,013
CASH FLOWS FROM INVESTING ACTIVITIES
Net cash used in investing activities									(1,771,949)	(951,103)	(993,358)
CASH FLOWS FROM FINANCING ACTIVITIES
Purchase of senior debt										(9,600)	(78)
Proceeds from issuance of common stock										155,581
Cash dividends paid on common stock									(45,995)
Repurchase of common stock									(22,010)
Net cash provided by financing activities									1,629,249	1,288,291	657,063
Net increase (decrease) in cash and cash equivalents									48,469	481,886	(218,282)
Cash and cash equivalents at beginning of period				730,811				248,925	730,811	248,925	467,207
Cash and cash equivalents at end of period	779,280				730,811				779,280	730,811	248,925
Cadence Bancorporation
CASH FLOWS FROM OPERATING ACTIVITIES
Net income									166,261	102,353	65,774
Adjustments to reconcile net income to net cash provided by operations:
Deferred income tax expense									358	1,084	(1,598)
Equity in undistributed income of subsidiaries									(125,727)	(103,390)	(64,424)
(Increase) decrease in other assets									(10,143)	3,892	3,043
Increase (decrease) in interest payable									5	3	(102)
Increase (decrease) in other liabilities									2,151	891	(504)
Net cash flows provided by operating activities									32,905	4,833	2,189
CASH FLOWS FROM INVESTING ACTIVITIES
Capital contributions to bank subsidiary										(50,000)
(Increase) decrease in limited partnership investments									(125)	(63)	463
Net cash used in investing activities									(125)	(50,063)	463
CASH FLOWS FROM FINANCING ACTIVITIES
Purchase of senior debt										(9,600)	(78)
Proceeds from issuance of common stock										155,581
Cash dividends paid on common stock									(45,995)
Repurchase of common stock									(22,010)
Net cash provided by financing activities									(68,005)	145,981	(78)
Net increase (decrease) in cash and cash equivalents									(35,225)	100,751	2,574
Cash and cash equivalents at beginning of period				$ 151,081				$ 50,330	151,081	50,330	47,756
Cash and cash equivalents at end of period	$ 115,856				$ 151,081				$ 115,856	$ 151,081	$ 50,330