Non-consolidated VIEs - Corporation's VI in non-consolidated VIEs and max exposure to loss (Details) - FNMA, GNMA, FHLMC VIE - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net
Assets	$ 143,965	$ 144,930
Maximum exposure to loss	143,965	144,930
Servicing assets
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net
Assets	113,793	115,718
Mortgage servicing rights
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net
Assets	113,793	115,718
Other assets
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net
Assets	30,172	29,212
Servicing advances
Variable Interest Entity, Nonconsolidated, Carrying Amount, Assets and Liabilities, Net
Assets	$ 30,172	$ 29,212