Accumulated Other Comprehensive Loss - Reclassifications (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Reclassification Out Of Accumulated Other Comprehensive Loss
Interest and dividends on investment securities (taxable)	$ 149	$ 489
Interest expense	(36,587)	(37,444)
Tax effect	(18,071)	(14,389)
Total net of tax	46,095	36,187
Total reclassifications, net of tax	(1,460)	(1,328)
Unrealized (losses) gains on AFS securities before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
Total reclassifications, net of tax	(13)
Non-credit impairment losses on AFS securities before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
Total reclassifications, net of tax	87
Unrealized losses on derivatives (cash flow hedges) before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
Total reclassifications, net of tax	(1,475)
Defined benefit pension plan
Reclassification Out Of Accumulated Other Comprehensive Loss
Amortization of net loss	(101)	(72)
Tax effect	42	29
Total reclassifications, net of tax	(59)	(43)
Reclassification Out of Accumulated Other Comprehensive Income (Loss)
Reclassification Out Of Accumulated Other Comprehensive Loss
Interest expense	(2,518)	(2,971)
Reclassification Out of Accumulated Other Comprehensive Income (Loss) | Unrealized (losses) gains on AFS securities before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
(Losses) gains on securities transactions, net	(23)	271
Tax effect	10	(101)
Total net of tax	(13)	170
Reclassification Out of Accumulated Other Comprehensive Income (Loss) | Non-credit impairment losses on AFS securities before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
Interest and dividends on investment securities (taxable)	149	489
Tax effect	(62)	(203)
Total net of tax	87	286
Reclassification Out of Accumulated Other Comprehensive Income (Loss) | Unrealized losses on derivatives (cash flow hedges) before tax
Reclassification Out Of Accumulated Other Comprehensive Loss
Interest expense	(2,518)	(2,971)
Tax effect	1,043	1,230
Total net of tax	$ (1,475)	$ (1,741)