Other Comprehensive Income - Schedule of Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before reclassification, net of tax	$ 35,712	$ (28,209)	$ (1,296)
Reclassification, net of tax	1,505	5,324	5,311
Net change before tax	53,045	(32,185)	7,611
Net change, tax	(15,828)	9,300	(3,596)
Other comprehensive income (loss), net	37,217	(22,885)	4,015
Unrealized Gains and Losses on AFS Securities
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before reclassification, before tax	54,723	(32,123)	1,485
Before reclassification, tax	(15,461)	9,191	(635)
Before reclassification, net of tax	39,262	(22,932)	850
Reclassification adjustment before tax	150	2,873	(264)
Reclassification, tax	(31)	(636)	108
Reclassification, net of tax	119	2,237	(156)
Net change before tax	54,873	(29,250)	1,221
Net change, tax	(15,492)	8,555	(527)
Other comprehensive income (loss), net	39,381	(20,695)	694
Unrealized Gains and Losses on Derivatives
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before reclassification, before tax	(1,380)	2,651	1,005
Before reclassification, tax	391	(777)	(429)
Before reclassification, net of tax	(989)	1,874	576
Reclassification adjustment before tax	1,808	3,493	8,579
Reclassification, tax	(517)	(999)	(3,551)
Reclassification, net of tax	1,291	2,494	5,028
Net change before tax	428	6,144	9,584
Net change, tax	(126)	(1,776)	(3,980)
Other comprehensive income (loss), net	302	4,368	5,604
Net (losses) gains arising during the period
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before reclassification, before tax	2,385	9,916	3,843
Before reclassification, tax	176	(2,765)	(1,121)
Before reclassification, net of tax	2,561	7,151	2,722
Amortization of prior service (cost) credit
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification adjustment before tax	135	(212)	(268)
Reclassification, tax	(42)	66	77
Reclassification, net of tax	93	(146)	(191)
Amortization of net loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification adjustment before tax	264	625	381
Reclassification, tax	(76)	(178)	(133)
Reclassification, net of tax	188	447	248
Net change
Accumulated Other Comprehensive Income (Loss) [Line Items]
Before reclassification, net of tax	(2,561)	(7,151)	(2,722)
Reclassification, net of tax	95	593	439
Net change before tax	(2,256)	(9,079)	(3,194)
Net change, tax	(210)	2,521	911
Other comprehensive income (loss), net	$ (2,466)	$ (6,558)	$ (2,283)