Loans - Schedule of Subsequently Defaulted TDRs (Detail) $ in Thousands	3 Months Ended
Mar. 31, 2017 USD ($) SecurityLoan	Mar. 31, 2016 USD ($) SecurityLoan
Accounts, Notes, Loans and Financing Receivable
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	101	94
Pre-modification outstanding recorded investment	$ 13,238	$ 45,189
Post-modification outstanding recorded investment	$ 13,165	$ 44,782
Number of loans \| SecurityLoan	162	51
Recorded investment	$ 28,416	$ 9,088
Non-Covered TDRs \| Commercial Loans \| Real Estate \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	10	9
Pre-modification outstanding recorded investment	$ 4,871	$ 1,228
Post-modification outstanding recorded investment	$ 4,854	$ 1,228
Number of loans \| SecurityLoan	16	9
Recorded investment	$ 13,583	$ 1,228
Non-Covered TDRs \| Commercial Loans \| Commercial and industrial \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	15	14
Pre-modification outstanding recorded investment	$ 435	$ 4,927
Post-modification outstanding recorded investment	$ 427	$ 4,737
Number of loans \| SecurityLoan	20	9
Recorded investment	$ 1,411	$ 1,627
Non-Covered TDRs \| Commercial Loans \| Energy-related \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	0	9
Pre-modification outstanding recorded investment	$ 0	$ 33,925
Post-modification outstanding recorded investment	$ 0	$ 33,925
Number of loans \| SecurityLoan	5	1
Recorded investment	$ 9,082	$ 2,250
Non-Covered TDRs \| Residential Mortgage \| Residential mortgage \| TDRs Occurring during the Period
Accounts, Notes, Loans and Financing Receivable
Number of loans \| SecurityLoan	4	15
Pre-modification outstanding recorded investment	$ 259	$ 3,295
Post-modification outstanding recorded investment	$ 241	$ 3,219
Number of loans \| SecurityLoan	22	15
Recorded investment	$ 1,793	$ 3,218
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	37	22
Pre-modification outstanding recorded investment	$ 6,622	$ 1,372
Post-modification outstanding recorded investment	$ 6,607	$ 1,316
Number of loans \| SecurityLoan	31	10
Recorded investment	$ 1,337	$ 595
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	13	0
Pre-modification outstanding recorded investment	$ 184	$ 0
Post-modification outstanding recorded investment	$ 174	$ 0
Number of loans \| SecurityLoan	43	0
Recorded investment	$ 517	$ 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	22	25
Pre-modification outstanding recorded investment	$ 867	$ 442
Post-modification outstanding recorded investment	$ 862	$ 357
Number of loans \| SecurityLoan	25	7
Recorded investment	$ 693	$ 170

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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=66008989&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=66008989&loc=SL6953682-111524

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