Fair Value Measurements - FV Option (Details) - USD ($) $ in Millions	Mar. 31, 2018	Dec. 31, 2017
Fair Value Measurements
Mortgage loans held for sale, fair value	$ 1,280	$ 1,580
Mortgage loans held for sale, unpaid principal balance	$ 1,240	$ 1,530

Represents the amount of unpaid principal balance of loans held for sale accounted under the fair value option.

No definition available.

Name:	hth_FairValueOptionLoansHeldForSaleUnpaidPrincipalBalance
Namespace Prefix:	hth_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant