Loans - Schedule of Subsequently Defaulted TDRs (Detail) $ in Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2017 USD ($) SecurityLoan	Sep. 30, 2016 USD ($) SecurityLoan	Sep. 30, 2017 USD ($) SecurityLoan	Sep. 30, 2016 USD ($) SecurityLoan
Accounts, Notes, Loans and Financing Receivable
Post-modification outstanding recorded investment	$ 24,586	$ 75,068	$ 51,517	$ 218,596
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	107	141	293	377
Pre-modification outstanding recorded investment	$ 23,821	$ 87,482	$ 49,445	$ 224,148
Post-modification outstanding recorded investment			$ 51,517	$ 218,596
Number of loans \| SecurityLoan	118	30	174	61
Recorded investment	$ 9,446	$ 2,820	$ 20,988	$ 11,217
Non-Covered TDRs \| Commercial Loans \| Commercial real estate- construction \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	2	0	2	1
Pre-modification outstanding recorded investment	$ 1,166	$ 0	$ 1,166	$ 28
Post-modification outstanding recorded investment	$ 1,164	$ 0	$ 1,164	$ 25
Number of loans \| SecurityLoan	2	0	2	0
Recorded investment	$ 1,164	$ 0	$ 1,164	$ 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	3	5	5	9
Pre-modification outstanding recorded investment	$ 717	$ 1,254	$ 2,447	$ 8,069
Post-modification outstanding recorded investment	$ 713	$ 1,254	$ 2,411	$ 8,043
Number of loans \| SecurityLoan	4	2	8	2
Recorded investment	$ 1,304	$ 238	$ 3,234	$ 239
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	10	6	21	13
Pre-modification outstanding recorded investment	$ 5,306	$ 9,512	$ 9,645	$ 14,668
Post-modification outstanding recorded investment	$ 5,298	$ 3,688	$ 11,505	$ 8,373
Number of loans \| SecurityLoan	11	2	16	3
Recorded investment	$ 2,206	$ 280	$ 4,929	$ 429
Non-Covered TDRs \| Commercial Loans \| Commercial and industrial \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	11	24	44	49
Pre-modification outstanding recorded investment	$ 11,650	$ 20,207	$ 18,743	$ 44,144
Post-modification outstanding recorded investment	$ 12,502	$ 20,175	$ 19,399	$ 43,083
Number of loans \| SecurityLoan	16	8	31	21
Recorded investment	$ 1,008	$ 1,434	$ 5,939	$ 7,476
Non-Covered TDRs \| Commercial Loans \| Energy-related \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	0	11	0	28
Pre-modification outstanding recorded investment	$ 0	$ 51,979	$ 0	$ 143,012
Post-modification outstanding recorded investment	$ 0	$ 45,682	$ 0	$ 145,298
Number of loans \| SecurityLoan	0	0	0	1
Recorded investment	$ 0	$ 0	$ 0	$ 1,394
Non-Covered TDRs \| Residential Mortgage \| Residential mortgage \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	7	7	16	31
Pre-modification outstanding recorded investment	$ 409	$ 937	$ 1,126	$ 4,784
Post-modification outstanding recorded investment	$ 392	$ 910	$ 1,030	$ 4,659
Number of loans \| SecurityLoan	13	1	18	5
Recorded investment	$ 819	$ 69	$ 1,243	$ 364
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	38	37	99	104
Pre-modification outstanding recorded investment	$ 3,495	$ 2,570	$ 13,573	$ 7,071
Post-modification outstanding recorded investment	$ 3,479	$ 2,371	$ 13,471	$ 6,805
Number of loans \| SecurityLoan	23	11	34	16
Recorded investment	$ 2,150	$ 602	$ 3,215	$ 1,037
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	11	19	36	63
Pre-modification outstanding recorded investment	$ 126	$ 273	$ 398	$ 691
Post-modification outstanding recorded investment	$ 114	$ 244	$ 279	$ 693
Number of loans \| SecurityLoan	26	0	34	0
Recorded investment	$ 242	$ 0	$ 308	$ 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	25	32	70	79
Pre-modification outstanding recorded investment	$ 952	$ 750	$ 2,347	$ 1,681
Post-modification outstanding recorded investment	$ 924	$ 744	$ 2,258	$ 1,617
Number of loans \| SecurityLoan	23	6	31	13
Recorded investment	$ 553	$ 197	$ 956	$ 278

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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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