Short-term Borrowings (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Short-term borrowings
Short-term borrowings	$ 1,216,649		$ 1,206,424
Hilltop Broker-Dealers
Short-term borrowings
Weighted average interest rate (as a percent)	3.08%		2.27%
Federal funds purchased.
Short-term borrowings
Short-term borrowings	$ 88,075		$ 101,775
Securities sold under agreement to repurchase.
Short-term borrowings
Short-term borrowings	459,574		539,149
FHLB notes
Short-term borrowings
Short-term borrowings	400,000		$ 250,000
Average balance during the year	$ 253,022	$ 435,531
Average interest rate during the year	2.04%	1.05%
Average interest rate at end of year (as a percent)	2.33%		1.30%
FHLB notes | Maximum
Short-term borrowings
Maturity term of debt	365 days
Short-term bank loans.
Short-term borrowings
Short-term borrowings	$ 269,000		$ 315,500
Federal funds purchased and securities sold under agreements to repurchase.
Short-term borrowings
Average balance during the year	$ 683,835	$ 549,425
Average interest rate during the year	1.76%	0.98%
Average interest rate at end of year (as a percent)	2.01%		1.21%
Securities underlying the agreements at end of period: Carrying value	$ 474,266		$ 581,636
Securities underlying the agreements at end of period: Estimated fair value	$ 490,719		$ 598,300