Comprehensive Income - Components of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Before Tax Amount
Other comprehensive loss, net	$ 5,838	$ (7,144)
Tax Benefit (Expense)
Other comprehensive loss, net	(1,689)	1,695
Net of Tax Amount
Other comprehensive income (loss)	4,149	(5,449)
Net unrealized gains (losses) on available for sale securities:
Before Tax Amount
Net unrealized holding (losses) gains arising during period	6,109	(7,502)
Reclassification adjustment for net gains arising during the period	0	0
Other comprehensive loss, net	6,109	(7,502)
Tax Benefit (Expense)
Net unrealized holding (losses) gains arising during period	(1,746)	1,770
Reclassification adjustment for net gains arising during the period	0	0
Other comprehensive loss, net	(1,746)	1,770
Net of Tax Amount
Net unrealized holding (losses) gains arising during period	4,363	(5,732)
Reclassification adjustment for net gains arising during the period	0	0
Other comprehensive income (loss)	4,363	(5,732)
Unrealized gains on derivatives
Before Tax Amount
Other comprehensive loss, net	(271)	358
Tax Benefit (Expense)
Other comprehensive loss, net	57	(75)
Net of Tax Amount
Other comprehensive income (loss)	$ (214)	$ 283