Impairment of Securities - Schedule of Temporary Impairment Losses, Investments (Detail) $ in Thousands		Jun. 30, 2019 USD ($) Security	Jun. 30, 2018 USD ($) Security
Schedule Of Held To Maturity Securities [Line Items]
Less than 12 Months: Fair Value		$ 712	$ 476,641
Less than 12 Months: Unrecognized Losses		2	7,824
12 Months or More: Fair Value		95,196	78,832
12 Months or More: Unrecognized Losses		$ 706	$ 2,548
Number of Securities | Security		96	371
Total: Fair Value		$ 95,908	$ 555,473
Total: Unrecognized Losses		708	10,372
Debt Securities [Member]
Schedule Of Held To Maturity Securities [Line Items]
Total: Unrecognized Losses		16	2,149
Debt Securities [Member] | Obligations of State and Political Subdivisions [Member]
Schedule Of Held To Maturity Securities [Line Items]
Less than 12 Months: Fair Value		274	86,678
Less than 12 Months: Unrecognized Losses		1	1,662
12 Months or More: Fair Value		7,149	3,151
12 Months or More: Unrecognized Losses		$ 15	$ 203
Number of Securities | Security		19	190
Total: Fair Value		$ 7,423	$ 89,829
Total: Unrecognized Losses		16	1,865
Debt Securities [Member] | Subordinated Debt [Member]
Schedule Of Held To Maturity Securities [Line Items]
Less than 12 Months: Fair Value			41,010
Less than 12 Months: Unrecognized Losses			$ 284
12 Months or More: Fair Value		9,347
12 Months or More: Unrecognized Losses		$ 168
Number of Securities | Security		5	7
Total: Fair Value		$ 9,347	$ 41,010
Total: Unrecognized Losses		168	284
Collateralized Mortgage Obligations Excluding Pass Through Securities [Member]
Schedule Of Held To Maturity Securities [Line Items]
Less than 12 Months: Fair Value			42,712
Less than 12 Months: Unrecognized Losses			753
12 Months or More: Fair Value			12,730
12 Months or More: Unrecognized Losses			$ 595
Number of Securities | Security			8
Total: Fair Value			$ 55,442
Total: Unrecognized Losses	[1]	168	1,348
Residential Pass-Through Securities [Member]
Schedule Of Held To Maturity Securities [Line Items]
Less than 12 Months: Fair Value		438	133,859
Less than 12 Months: Unrecognized Losses		1	2,258
12 Months or More: Fair Value		76,848	61,760
12 Months or More: Unrecognized Losses		$ 517	$ 1,747
Number of Securities | Security		70	131
Total: Fair Value		$ 77,286	$ 195,619
Total: Unrecognized Losses	[1]	518	4,005
Commercial Pass-Through Securities [Member]
Schedule Of Held To Maturity Securities [Line Items]
Less than 12 Months: Fair Value			172,382
Less than 12 Months: Unrecognized Losses			2,867
12 Months or More: Fair Value		1,852	1,191
12 Months or More: Unrecognized Losses		$ 6	$ 3
Number of Securities | Security		2	35
Total: Fair Value		$ 1,852	$ 173,573
Total: Unrecognized Losses	[1]	$ 6	$ 2,870

[1] (1)Government-sponsored enterprises.