Intangible Assets and Goodwill - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2015	Dec. 31, 2016	Dec. 31, 2015
Finite-Lived Intangible Assets [Line Items]
Weighted-average life		6 years 8 months 12 days
Goodwill impairment loss		$ 0	$ 368
Community Banks [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment loss		$ 0	$ 368
Community Banks [Member] | Other Noninterest Expense [Member]
Finite-Lived Intangible Assets [Line Items]
Goodwill impairment loss	$ 368
Customer Related Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average life		6 years 10 months 24 days
Core Deposit Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average life		6 years 9 months 18 days
Mortgage Servicing Intangibles [Member]
Finite-Lived Intangible Assets [Line Items]
Weighted-average life		2 years