Noninterest Income and Expense - Components of Other Noninterest Income (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Statement [Abstract]
Service charges on deposit accounts									$ 14,365	$ 14,276	$ 11,811
ATM and interchange fees									15,859	13,364	9,651
Other service fees									3,121	2,977	2,206
Mortgage banking service fees									2,065	2,164	1,869
Change in value of mortgage servicing rights									(2,184)	(701)	(1,301)
Total service charges and fees									33,226	32,080	24,236
Gain on sale of loans									4,037	3,064	2,032
Commissions on sale of non-deposit investment products									2,329	3,349	2,995
Increase in cash value of life insurance									2,717	2,786	1,953
Change in indemnification asset									(493)	(207)	(856)
Gain on sale of foreclosed assets									262	991	2,153
Sale of customer checks									408	492	450
Lease brokerage income									711	712	504
Gain (loss) on disposal of fixed assets									(147)	(129)	49
Gain on life insurance death benefit									238	155
Other									1,275	2,054	1,000
Total other noninterest income									11,337	13,267	10,280
Total noninterest income	$ 12,462	$ 11,066	$ 11,245	$ 9,790	$ 11,445	$ 11,642	$ 12,080	$ 10,180	$ 44,563	$ 45,347	$ 34,516