Non-Covered Loans and Allowance for Non-Covered Loan Losses - TDRs (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2016 USD ($) item	Dec. 31, 2015 USD ($) item	Dec. 31, 2014 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	1	3	4
TDR at extension	$ 1,196	$ 1,248	$ 3,215
TDR modification, end of period	$ 944	$ 1,122	$ 3,158
Number of TDRs granted in preceding twelve months for which payment was at least 30 days past due | item	1	2
TDR modifications, in which a payment was at least 30 days past due	$ 1,196	$ 1,159
TDR with payment at least 30 days past due	$ 944	$ 1,040
Noncovered | Secured | Payment Term Extension
TDRs, Non-covered loans
Number of TDR loans granted | item	1	1	1
TDR at extension	$ 1,196	$ 89	$ 2,465
TDR modification, end of period	$ 944	$ 82	$ 2,465
Number of TDRs granted in preceding twelve months for which payment was at least 30 days past due | item	1
TDR modifications, in which a payment was at least 30 days past due	$ 1,196
TDR with payment at least 30 days past due	$ 944
Noncovered | Secured by Commercial Properties | Payment Term Extension
TDRs, Non-covered loans
Number of TDR loans granted | item		1	1
TDR at extension		$ 1,083	$ 345
TDR modification, end of period		$ 1,040	$ 317
Number of TDRs granted in preceding twelve months for which payment was at least 30 days past due | item		1
TDR modifications, in which a payment was at least 30 days past due		$ 1,083
TDR with payment at least 30 days past due		$ 1,040
Noncovered | Secured by Residential Properties | Payment Term Extension
TDRs, Non-covered loans
Number of TDR loans granted | item			1
TDR at extension			$ 262
TDR modification, end of period			$ 248
Noncovered | Commercial construction loans and land development | Payment Term Extension
TDRs, Non-covered loans
Number of TDR loans granted | item		1	1
TDR at extension		$ 76	$ 143
TDR modification, end of period			$ 128
Number of TDRs granted in preceding twelve months for which payment was at least 30 days past due | item		1
TDR modifications, in which a payment was at least 30 days past due		$ 76