Derivative Financial Instruments (Offsetting Derivatives) (Detail) - USD ($) $ in Thousands	Jun. 30, 2019	Dec. 31, 2018
Derivative [Line Items]
Derivative instrument assets, Gross Amount	$ 6,578	$ 9,928
Derivative instrument asset, Amount Offset	40,400
Derivative Asset	2,706	2,497
Liability Derivatives, Fair Value, Gross Liability	10,615	2,566
Derivative liability	2,944	71
Hedge Accounting Positions [Member]
Derivative [Line Items]
Derivative instrument assets, Gross Amount	4,515	3,050
Derivative instrument asset, Amount Offset, Total	(970)	(88)
Derivative instrument asset, Amount Offset	1,505	567
Derivative Asset	2,040	2,395
Liability Derivatives, Fair Value, Gross Liability	0	0
Derivative instrument liability, Amount Offset, Total	0	0
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	0	0
Derivative liability	0	0
Non-Hedged Accounting Positions [Member]
Derivative [Line Items]
Derivative instrument assets, Gross Amount	2,063	6,878
Derivative instrument asset, Amount Offset, Total	(1,397)	(2,407)
Derivative instrument asset, Amount Offset	0	4,369
Derivative Asset	666	102
Liability Derivatives, Fair Value, Gross Liability	10,615	2,566
Derivative instrument liability, Amount Offset, Total	(2,367)	(2,495)
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	(5,304)	0
Derivative liability	2,944	71
Subject to and not subject to Master Netting Agreements [Member]
Derivative [Line Items]
Derivative instrument asset, Amount Offset, Total	(2,367)	(2,495)
Derivative instrument asset, Amount Offset	1,505	4,936
Derivative Asset	138,561	38,847
Derivative instrument liability, Amount Offset, Total	(2,367)	(2,495)
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	(5,304)	0
Derivative liability	$ 6,374	$ 36,515