Fair Values of Assets and Liabilities (Summary of Assets Measured at Fair Value on a Nonrecurring Basis) (Detail) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
	Jun. 30, 2017	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans—collateral based	$ 79,318	$ 79,318	$ 90,516	$ 95,976
Fair Value Losses Recognized, Impaired loans—collateral based	4,609	6,330
Fair Value Losses Recognized, Other real estate owned	265	1,270
Fair Value Losses Recognized, Total	4,874	7,600
Fair Value, Measurements, Nonrecurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans—collateral based	57,259	57,259
Other real estate owned, including covered other real estate owned	42,617	42,617
Total	99,876	99,876
Fair Value, Measurements, Nonrecurring | Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans—collateral based	0	0
Other real estate owned, including covered other real estate owned	0	0
Total	0	0
Fair Value, Measurements, Nonrecurring | Level 2
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans—collateral based	0	0
Other real estate owned, including covered other real estate owned	0	0
Total	0	0
Fair Value, Measurements, Nonrecurring | Level 3
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Impaired loans—collateral based	57,259	57,259
Other real estate owned, including covered other real estate owned	42,617	42,617
Total	$ 99,876	$ 99,876