Accumulated Other Comprehensive Income (Loss) - Schedule of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (34,797)	$ (31,555)	$ (44,466)
Other comprehensive income (loss) before reclassifications	(32,953)	(4,473)	20,492
Amounts reclassified from accumulated other comprehensive income (loss)	8,378	1,231	(7,581)
Net other comprehensive income (loss)	(24,575)	(3,242)	12,911
Ending Balance	(59,372)	(34,797)	(31,555)
Accumulated Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(3,806)	(748)	(21,108)
Other comprehensive income (loss) before reclassifications	(31,513)	554	26,391
Amounts reclassified from accumulated other comprehensive income (loss)	(3,693)	(3,612)	(6,031)
Net other comprehensive income (loss)	(35,206)	(3,058)	20,360
Ending Balance	(39,012)	(3,806)	(748)
Accumulated Unrealized Gains and Losses on Held-to-Maturity Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(14,480)	(15,776)	(16,767)
Amounts reclassified from accumulated other comprehensive income (loss)	1,170	1,296	991
Net other comprehensive income (loss)	1,170	1,296	991
Ending Balance	(13,310)	(14,480)	(15,776)
Accumulated Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(9,276)	(5,935)	(190)
Other comprehensive income (loss) before reclassifications	(1,440)	(5,027)	(5,899)
Amounts reclassified from accumulated other comprehensive income (loss)	4,001	1,686	154
Net other comprehensive income (loss)	2,561	(3,341)	(5,745)
Ending Balance	(6,715)	(9,276)	(5,935)
Accumulated Defined Benefit Pension Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(7,235)	(9,096)	(6,401)
Amounts reclassified from accumulated other comprehensive income (loss)	6,900	1,861	(2,695)
Net other comprehensive income (loss)	6,900	1,861	(2,695)
Ending Balance	$ (335)	$ (7,235)	$ (9,096)