Loans - Schedule of Subsequently Defaulted TDRs (Detail) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2017 USD ($) SecurityLoan	Jun. 30, 2016 USD ($) SecurityLoan	Jun. 30, 2017 USD ($) SecurityLoan	Jun. 30, 2016 USD ($) SecurityLoan
Accounts, Notes, Loans and Financing Receivable
Post-modification outstanding recorded investment	$ 17,892	$ 135,524	$ 28,398	$ 165,283
Threshold period for loans in default (in days)	30 days
Non-Covered TDRs \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	124	151	206	236
Pre-modification outstanding recorded investment	$ 18,453	$ 119,083	$ 29,206	$ 157,121
Post-modification outstanding recorded investment	$ 17,892	$ 135,524	$ 28,398	$ 165,283
Number of loans \| SecurityLoan	81	65	168	115
Recorded investment	$ 18,671	$ 6,440	$ 22,744	$ 9,642
Non-Covered TDRs \| Commercial Loans \| Commercial real estate- construction \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	1	0	1	1
Pre-modification outstanding recorded investment	$ 275	$ 0	$ 275	$ 28
Post-modification outstanding recorded investment	$ 275	$ 0	$ 275	$ 26
Number of loans \| SecurityLoan	0	0	2	0
Recorded investment	$ 0	$ 0	$ 132	$ 0
Non-Covered TDRs \| Commercial Loans \| Commercial real estate- owner-occupied \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	1	3	2	5
Pre-modification outstanding recorded investment	$ 32	$ 794	$ 1,730	$ 1,069
Post-modification outstanding recorded investment	$ 31	$ 785	$ 1,698	$ 1,050
Number of loans \| SecurityLoan	5	0	7	0
Recorded investment	$ 2,297	$ 0	$ 2,404	$ 0
Non-Covered TDRs \| Commercial Loans \| Commercial real estate- non-owner-occupied \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	6	6	11	10
Pre-modification outstanding recorded investment	$ 2,721	$ 10,777	$ 4,409	$ 11,516
Post-modification outstanding recorded investment	$ 2,795	$ 10,047	$ 4,465	$ 10,749
Number of loans \| SecurityLoan	9	4	14	8
Recorded investment	$ 5,640	$ 1,358	$ 6,406	$ 1,377
Non-Covered TDRs \| Commercial Loans \| Commercial and industrial \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	24	16	33	28
Pre-modification outstanding recorded investment	$ 9,028	$ 19,496	$ 9,254	$ 24,018
Post-modification outstanding recorded investment	$ 8,551	$ 19,353	$ 8,747	$ 23,632
Number of loans \| SecurityLoan	17	5	25	8
Recorded investment	$ 8,081	$ 758	$ 8,239	$ 3,273
Non-Covered TDRs \| Commercial Loans \| Energy-related \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	0	19	0	25
Pre-modification outstanding recorded investment	$ 0	$ 82,882	$ 0	$ 110,443
Post-modification outstanding recorded investment	$ 0	$ 100,205	$ 0	$ 119,890
Number of loans \| SecurityLoan	0	1	0	1
Recorded investment	$ 0	$ 2,250	$ 0	$ 2,250
Non-Covered TDRs \| Residential Mortgage \| Residential mortgage \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	6	10	10	25
Pre-modification outstanding recorded investment	$ 521	$ 1,438	$ 780	$ 4,733
Post-modification outstanding recorded investment	$ 492	$ 1,438	$ 730	$ 4,692
Number of loans \| SecurityLoan	5	4	21	7
Recorded investment	$ 454	$ 480	$ 1,854	$ 536
Non-Covered TDRs \| Consumer and Other Loans \| Consumer - home equity \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	33	36	66	57
Pre-modification outstanding recorded investment	$ 4,820	$ 2,750	$ 10,851	$ 3,928
Post-modification outstanding recorded investment	$ 4,807	$ 2,750	$ 10,771	$ 3,916
Number of loans \| SecurityLoan	19	17	37	24
Recorded investment	$ 1,532	$ 1,112	$ 2,488	$ 1,608
Non-Covered TDRs \| Consumer and Other Loans \| Consumer - Indirect Automobile \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	23	0	33	0
Pre-modification outstanding recorded investment	$ 224	$ 0	$ 360	$ 0
Post-modification outstanding recorded investment	$ 114	$ 0	$ 222	$ 0
Number of loans \| SecurityLoan	9	0	33	0
Recorded investment	$ 75	$ 0	$ 328	$ 0
Non-Covered TDRs \| Consumer and Other Loans \| Consumer - other \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	30	61	50	85
Pre-modification outstanding recorded investment	$ 832	$ 946	$ 1,547	$ 1,386
Post-modification outstanding recorded investment	$ 827	$ 946	$ 1,490	$ 1,328
Number of loans \| SecurityLoan	17	34	29	67
Recorded investment	$ 592	$ 482	$ 893	$ 598

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Number of financing receivables that have been modified by troubled debt restructurings.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 33
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953676-111524

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 310
-SubTopic 10
-Section 50
-Paragraph 34
-URI http://asc.fasb.org/extlink&oid=84173941&loc=SL6953682-111524

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