Comprehensive Income - Components of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Before Tax Amount
Other comprehensive loss, net	$ 7,427	$ (2,136)	$ 13,265	$ (9,280)
Tax Benefit (Expense)
Other comprehensive loss, net	(1,930)	499	(3,619)	2,194
Net of Tax Amount
Other comprehensive income (loss)	5,497	(1,637)	9,646	(7,086)
Net unrealized gains (losses) on available for sale securities:
Before Tax Amount
Net unrealized holding gains (losses) arising during period	7,852	(2,203)	13,961	(9,705)
Reclassification adjustment for net gains arising during the period	0	0	0	0
Other comprehensive loss, net	7,852	(2,203)	13,961	(9,705)
Tax Benefit (Expense)
Net unrealized holding gains (losses) arising during period	(2,076)	513	(3,822)	2,283
Reclassification adjustment for net gains arising during the period	0	0	0	0
Other comprehensive loss, net	(2,076)	513	(3,822)	2,283
Net of Tax Amount
Net unrealized holding gains (losses) arising during period	5,776	(1,690)	10,139	(7,422)
Reclassification adjustment for net gains arising during the period	0	0	0	0
Other comprehensive income (loss)	5,776	(1,690)	10,139	(7,422)
Unrealized (losses) gains on derivatives
Before Tax Amount
Other comprehensive loss, net	(425)	67	(696)	425
Tax Benefit (Expense)
Other comprehensive loss, net	146	(14)	203	(89)
Net of Tax Amount
Other comprehensive income (loss)	$ (279)	$ 53	$ (493)	$ 336