Changes in Accumulated Other Comprehensive Income (Loss) By Component (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2020	Mar. 31, 2019
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 1,052,795	$ 956,816
Unrealized gains (losses) arising during period, before tax	(36,795)	10,878
Income tax effect	9,717	(2,828)
Other comprehensive income (loss) before reclassifications	(27,078)	8,050
Reclassification adjustments for losses (gains) included in net income, before tax	(2,496)	(413)
Income tax effect	649	107
Amounts reclassified from accumulated other comprehensive income (loss) to net income	(1,847)	(306)
Other comprehensive income (loss), net of income tax effect	(28,925)	7,744
Ending balance	964,636	978,373
Unrealized Gains (Losses) on Available for Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	14,287	(21,741)
Unrealized gains (losses) arising during period, before tax	(9,098)	17,817
Income tax effect	2,366	(4,632)
Other comprehensive income (loss) before reclassifications	(6,732)	13,185
Reclassification adjustments for losses (gains) included in net income, before tax	(3,974)	0
Income tax effect	1,033	0
Amounts reclassified from accumulated other comprehensive income (loss) to net income	(2,941)	0
Other comprehensive income (loss), net of income tax effect	(9,673)	13,185
Ending balance	4,614	(8,556)
Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(15,537)	(922)
Unrealized gains (losses) arising during period, before tax	(27,697)	(6,939)
Income tax effect	7,351	1,804
Other comprehensive income (loss) before reclassifications	(20,346)	(5,135)
Reclassification adjustments for losses (gains) included in net income, before tax	1,478	(413)
Income tax effect	(384)	107
Amounts reclassified from accumulated other comprehensive income (loss) to net income	1,094	(306)
Other comprehensive income (loss), net of income tax effect	(19,252)	(5,441)
Ending balance	(34,789)	(6,363)
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(1,250)	(22,663)
Other comprehensive income (loss), net of income tax effect	(28,925)	7,744
Ending balance	$ (30,175)	$ (14,919)

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