Stockholders' Equity - Summary of Line Items in Consolidated Income Statements Affected by Amounts Reclassified from Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Tax effect	$ (38,304)	$ (66,465)	$ (52,510)
Net income	131,461	175,722	$ 163,356
Amount Reclassified from Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Net income	(4,251)	2,396
Amount Reclassified from Accumulated Other Comprehensive Income [Member] | Available for Sale Securities [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Gain on sale of AFS securities	165
Tax effect	(58)
Net income	107
Amount Reclassified from Accumulated Other Comprehensive Income [Member] | Unrealized Losses on Securities Available for Sale Transferred to Held to Maturity [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of unrealized net loss on securities transferred to HTM	(3,530)	(3,297)
Tax effect	1,236	1,154
Net income	(2,294)	(2,143)
Amount Reclassified from Accumulated Other Comprehensive Income [Member] | Employee Benefit Plans [Member]
Reclassification Adjustment out of Accumulated Other Comprehensive Income [Line Items]
Amortization of defined benefit pension and post-retirement items	(3,175)	(390)
Tax effect	1,111	137
Net income	$ (2,064)	$ (253)