Basis of Presentation - Correction of Prior Period Balances (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Noninterest income - Other income	$ 6,051	$ 4,578	$ 11,246	$ 9,149
Noninterest expense - Other operating expense	$ 9,512	8,081	18,631	$ 15,741
Immaterial error, cash servicing fees
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Noninterest income - Other income		4,578	9,149
Noninterest expense - Other operating expense		8,081	15,741
Immaterial error, cash servicing fees | As originally reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Noninterest income - Other income		3,920	7,892
Noninterest expense - Other operating expense		7,423	14,484
Immaterial error, cash servicing fees | Adjustments
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Noninterest income - Other income		658	1,257
Noninterest expense - Other operating expense		$ 658	$ 1,257