Condensed Financial Information of Fidelity Southern Corporation (Parent Company Only) - Cash Flows (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Operating Activities:
Net income	$ 39,796	$ 38,766	$ 39,135
Adjustments to reconcile net income to net cash provided by operating activities:
(Increase) decrease in other assets	4,611	(1,969)	(464)
(Decrease) increase in other liabilities	159	(10,535)	3,292
Net cash provided by (used in) operating activities	155,201	(29,508)	2,955
Investing Activities:
Net cash used in investing activities	(257,319)	(205,080)	(229,480)
Financing Activities:
Repurchase of common stock	(1,673)	(821)	(796)
Proceeds from the issuance of common stock, net	9,295	10,153	6,348
Net cash provided by financing activities	138,709	298,166	241,053
Net increase in cash and cash equivalents	36,591	63,578	14,528
Parent Company
Operating Activities:
Net income	39,796	38,766	39,135
Adjustments to reconcile net income to net cash provided by operating activities:
Equity in undistributed income of subsidiaries	(31,272)	(33,681)	(37,640)
(Increase) decrease in other assets	(860)	(1,466)	371
(Decrease) increase in other liabilities	(76)	69	(118)
Share based compensation included in undistributed earnings	4,624	3,544	1,468
Net cash provided by (used in) operating activities	12,212	7,232	3,216
Investing Activities:
Net increase in investment in subsidiaries	(4,624)	(1,729)	(1,091)
Net cash used in investing activities	(4,624)	(1,729)	(1,091)
Financing Activities:
Repurchase of common stock	(1,673)	(821)	(796)
Proceeds from the issuance of common stock, net	9,295	10,153	6,348
Cash dividends paid	(12,748)	(12,187)	(8,630)
Net cash provided by financing activities	(5,126)	(2,855)	(3,078)
Net increase in cash and cash equivalents	2,462	2,648	(953)
Cash and cash equivalents, beginning of year	6,659	4,011	4,964
Cash and cash equivalents, end of year	$ 9,121	$ 6,659	$ 4,011