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, 2019	Sep. 30, 2018	Dec. 31, 2018
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Mortgage servicing rights	$ 70,241		$ 81,012
Mortgage banking, net	177	$ (669)
Equity securities	13,000		0
Investment securities gains (losses), net	15,096		1,568
Fair Value, Inputs, Level 3
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Equity securities	13,444		0
Investment securities gains (losses), net	13,444		0
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 2
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
OREO(c)	2,413		2,200
Other noninterest expense	(1,453)		(1,545)
Fair Value, Nonrecurring [Member] | Fair Value, Inputs, Level 3
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Impaired loans(a)	51,501		26,191
Provision for credit losses(b)	(60,627)		(14,521)
Mortgage servicing rights	70,241		81,012
Mortgage banking, net	(177)		$ 545
Equity securities	13,444
Investment securities gains (losses), net	$ 13,444