Non-Covered Loans and Allowance for Non-Covered Loan Losses - TDRs (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($) item	Mar. 31, 2016 USD ($) item
AB Note | Minimum | PlainsCapital
TDRs, Non-covered loans
Number of loans into which a single loan is reconfigured | item	2
Noncovered | Payment Term Extension
TDRs, Non-covered loans
Number of TDR loans granted | item	2	1
TDR at extension	$ 2,838	$ 1,196
TDR modification, end of period	$ 2,812	$ 1,196
Number of TDRs granted in preceding twelve months for which payment was at least 30 days past due | item	1	1
TDR modifications, in which a payment was at least 30 days past due	$ 1,481	$ 1,084
TDR with payment at least 30 days past due	$ 1,470	$ 1,017
Noncovered | Secured | Payment Term Extension
TDRs, Non-covered loans
Number of TDR loans granted | item	1	1
TDR at extension	$ 1,357	$ 1,196
TDR modification, end of period	$ 1,342	$ 1,196
Noncovered | Secured by Commercial Properties | Payment Term Extension
TDRs, Non-covered loans
Number of TDR loans granted | item	1
TDR at extension	$ 1,481
TDR modification, end of period	$ 1,470
Number of TDRs granted in preceding twelve months for which payment was at least 30 days past due | item	1	1
TDR modifications, in which a payment was at least 30 days past due	$ 1,481	$ 1,084
TDR with payment at least 30 days past due	$ 1,470	$ 1,017