Accumulated Other Comprehensive Loss - Schedule of Changes in Accumulated Other Comprehensive Loss After Tax (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Accumulated Other Comprehensive Income (Loss)
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	$ (45,695)
Other comprehensive income (loss) before reclassifications	1,672
Amounts reclassified from other comprehensive income (loss)	1,328
Total other comprehensive income (loss)	3,000	$ (2,167)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(42,695)
Unrealized Gains and Losses on Available for Sale (AFS) Securities
Accumulated Other Comprehensive Income (Loss)
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	(5,336)
Other comprehensive income (loss) before reclassifications	8,283
Amounts reclassified from other comprehensive income (loss)	(170)
Total other comprehensive income (loss)	8,113
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	2,777
Non-credit Impairment Losses on AFS Securities
Accumulated Other Comprehensive Income (Loss)
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	(520)
Other comprehensive income (loss) before reclassifications	(59)
Amounts reclassified from other comprehensive income (loss)	(286)
Total other comprehensive income (loss)	(345)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(865)
Unrealized Gains and (Losses) on Derivatives
Accumulated Other Comprehensive Income (Loss)
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	(17,644)
Other comprehensive income (loss) before reclassifications	(6,552)
Amounts reclassified from other comprehensive income (loss)	1,741
Total other comprehensive income (loss)	(4,811)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(22,455)
Total Accumulated Other Comprehensive Loss
Accumulated Other Comprehensive Income (Loss)
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	(45,695)
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	(42,695)
Defined Benefit Pension Plan
Accumulated Other Comprehensive Income (Loss)
Total Accumulated Other Comprehensive Income (Loss), Beginning Balance	(22,195)
Other comprehensive income (loss) before reclassifications	0
Amounts reclassified from other comprehensive income (loss)	43
Total other comprehensive income (loss)	43
Total Accumulated Other Comprehensive Income (Loss), Ending Balance	$ (22,152)