Fair Value Measurements, Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details) - USD ($) $ in Thousands	9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Mortgage servicing rights	$ 45,303		$ 72,532
Mortgage banking, net	18,481	$ 177
Equity securities	13,000		13,000
Investment securities gains (losses), net	15,090		15,090
Fair Value, Inputs, Level 3
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Equity securities	13,444		13,444
Investment securities gains (losses), net	13,444		13,444
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 2
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
OREO(b)	10,953		3,565
Other noninterest expense	(7,339)		(1,860)
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 3
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Individually evaluated loans(a)	117,451		45,792
Provision for credit losses	(96,856)		(66,172)
Mortgage servicing rights	45,303		72,532
Mortgage banking, net	$ (18,481)		(63)
Equity securities			13,444
Investment securities gains (losses), net			$ 13,444