Note Non-consolidated VIEs (Carrying amount and classification of assets related to the Corporation's VI in non-consolidated VIEs and max exposure to loss) (Detail) - FNMA, GNMA, FHLMC VIE - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net
Assets	$ 172,905	$ 174,268
Maximum exposure to loss	172,905	174,268
Servicing assets
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net
Assets	133,108	136,280
Mortgage servicing rights
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net
Assets	133,108	136,280
Other assets
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net
Assets	39,797	37,988
Servicing advances
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net
Assets	$ 39,797	$ 37,988