Changes in Accumulated Other Comprehensive Income (Loss) By Component (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	$ 1,188,721	$ 964,636	$ 1,117,086	$ 1,052,795
Unrealized gains (losses) arising during period, before tax	598	28,946	13,313	(7,849)
Income tax effect	(156)	(7,498)	(3,462)	2,219
Other comprehensive income (loss) before reclassifications	442	21,448	9,851	(5,630)
Reclassification adjustments for (gains) losses included in net income, before tax	(766)	(1,635)	1,594	(4,132)
Income tax effect	199	397	(415)	1,047
Amounts reclassified from accumulated other comprehensive income (loss) to net income	(567)	(1,238)	1,179	(3,085)
Other comprehensive income (loss), net of income tax effect	(125)	20,210	11,030	(8,715)
Ending balance	1,250,729	1,007,847	1,250,729	1,007,847
Total
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	5,391	(30,175)	(5,764)	(1,250)
Other comprehensive income (loss), net of income tax effect	(125)	20,210	11,030	(8,715)
Ending balance	5,266	(9,965)	5,266	(9,965)
Unrealized Gains (Losses) on Available for Sale Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	6,169	4,614	23,312	14,287
Unrealized gains (losses) arising during period, before tax	592	35,315	992	26,217
Income tax effect	(154)	(9,182)	(258)	(6,816)
Other comprehensive income (loss) before reclassifications	438	26,133	734	19,401
Reclassification adjustments for (gains) losses included in net income, before tax	(1,812)	(4,353)	(25,378)	(8,328)
Income tax effect	471	1,131	6,598	2,165
Amounts reclassified from accumulated other comprehensive income (loss) to net income	(1,341)	(3,222)	(18,780)	(6,163)
Other comprehensive income (loss), net of income tax effect	(903)	22,911	(18,046)	13,238
Ending balance	5,266	27,525	5,266	27,525
Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning balance	(778)	(34,789)	(29,076)	(15,537)
Unrealized gains (losses) arising during period, before tax	6	(6,369)	12,321	(34,066)
Income tax effect	(2)	1,684	(3,204)	9,035
Other comprehensive income (loss) before reclassifications	4	(4,685)	9,117	(25,031)
Reclassification adjustments for (gains) losses included in net income, before tax	1,046	2,718	26,972	4,196
Income tax effect	(272)	(734)	(7,013)	(1,118)
Amounts reclassified from accumulated other comprehensive income (loss) to net income	774	1,984	19,959	3,078
Other comprehensive income (loss), net of income tax effect	778	(2,701)	29,076	(21,953)
Ending balance	$ 0	$ (37,490)	$ 0	$ (37,490)