Remaining Contractual Maturities Of Repurchase Agreements (Detail) $ in Thousands	Jun. 30, 2016 USD ($)
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	$ 1,540,650
U.S. Treasury
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	296,222
U.S. Agencies
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	1,244,428
Maturity Overnight and Continuous
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	1,537,550
Maturity Overnight and Continuous | U.S. Treasury
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	296,222
Maturity Overnight and Continuous | U.S. Agencies
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	1,241,328
Over 90 Days [Member]
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	3,100
Over 90 Days [Member] | U.S. Agencies
Assets Sold under Agreements to Repurchase [Line Items]
Total repurchase agreements	$ 3,100