Fair Value Accounting - Assets Measured at Fair Value on Nonrecurring Basis (Detail) - USD ($) $ in Thousands		Jun. 30, 2017	Dec. 31, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded	[1]	$ 8,295	$ 10,909
Impaired loans without specific valuation allowance	[2]	97,339	88,300
Other Repossessed Assets		31,000	47,800
Impaired Financing Receivables, With No related Allowance, Balances with Charge-offs		20,800	27,600
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded		4,417	6,670
Impaired loans without specific valuation allowance	[3]	76,575	60,738
Other Repossessed Assets		30,988	47,815
Fair Value, Measurements, Nonrecurring [Member] | Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded		0	0
Impaired loans without specific valuation allowance	[3]	0	0
Other Repossessed Assets		0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded		0	0
Impaired loans without specific valuation allowance	[3]	0	0
Other Repossessed Assets		0	0
Fair Value, Measurements, Nonrecurring [Member] | Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans with an allowance recorded		4,417	6,670
Impaired loans without specific valuation allowance	[3]	76,575	60,738
Other Repossessed Assets		$ 30,988	$ 47,815

[1] Includes TDR loans of $6.9 million and $2.5 million at June 30, 2017 and December 31, 2016, respectively.

[2] Includes TDR loans of $48.3 million and $58.3 million at June 30, 2017 and December 31, 2016, respectively.

[3] Certain assets are measured at fair value on a nonrecurring basis. That is, the assets are not measured at fair value on an ongoing basis, but are subject to fair value adjustments in certain circumstances (for example, when there is evidence of impairment). The following table presents such assets carried on the balance sheet by caption and by level within the ASC 825 hierarchy: Fair Value Measurements at the End of the Reporting Period Using Total Quoted Prices in Active Markets for Identical Assets(Level 1) Active Markets for Similar Assets(Level 2) Unobservable Inputs(Level 3) (in thousands)As of June 30, 2017: Impaired loans with specific valuation allowance $4,417 $— $— $4,417Impaired loans without specific valuation allowance (1) 76,575 — — 76,575Other assets acquired through foreclosure 30,988 — — 30,988As of December 31, 2016: Impaired loans with specific valuation allowance $6,670 $— $— $6,670Impaired loans without specific valuation allowance (1) 60,738 — — 60,738Other assets acquired through foreclosure 47,815 — — 47,815(1)Net of loan balances with charge-offs of $20.8 million and $27.6 million as of June 30, 2017 and December 31, 2016, respectively