Accumulated Other Comprehensive Income (Loss) - Schedule of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (29,585)	$ (24,242)	$ (34,797)	$ (31,555)
Other comprehensive income (loss) before reclassifications	5,428	(14,499)	9,810	(6,473)
Amounts reclassified from accumulated other comprehensive income (loss)	540	679	1,370	(34)
Net other comprehensive income (loss)	5,968	(13,820)	11,180	(6,507)
Ending Balance	(23,617)	(38,062)	(23,617)	(38,062)
Accumulated Unrealized Gains and Losses on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	6,777	9,079	(3,806)	(748)
Other comprehensive income (loss) before reclassifications	8,208	(16,704)	19,490	(5,189)
Amounts reclassified from accumulated other comprehensive income (loss)	(1,202)	(326)	(1,901)	(2,014)
Net other comprehensive income (loss)	7,006	(17,030)	17,589	(7,203)
Ending Balance	13,783	(7,951)	13,783	(7,951)
Accumulated Unrealized Gains and Losses on Held-to-Maturity Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(14,174)	(15,373)	(14,480)	(15,776)
Amounts reclassified from accumulated other comprehensive income (loss)	307	283	613	686
Net other comprehensive income (loss)	307	283	613	686
Ending Balance	(13,867)	(15,090)	(13,867)	(15,090)
Accumulated Gains and Losses on Cash Flow Hedges [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(15,387)	(9,309)	(9,276)	(5,935)
Other comprehensive income (loss) before reclassifications	(2,780)	2,205	(9,680)	(1,284)
Amounts reclassified from accumulated other comprehensive income (loss)	983	272	1,772	387
Net other comprehensive income (loss)	(1,797)	2,477	(7,908)	(897)
Ending Balance	(17,184)	(6,832)	(17,184)	(6,832)
Accumulated Defined Benefit Pension Plans [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(6,801)	(8,639)	(7,235)	(9,096)
Amounts reclassified from accumulated other comprehensive income (loss)	452	450	886	907
Net other comprehensive income (loss)	452	450	886	907
Ending Balance	$ (6,349)	$ (8,189)	$ (6,349)	$ (8,189)