Fair Value Measurements, Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Mortgage servicing rights	$ 73,858		$ 81,012
Mortgage Servicing Rights (MSR) Impairment (Recovery)	121	$ (474)
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Other Real Estate Owned Fair Value Disclosure	183		2,200
Foreclosure / OREO expense, net	(148)		(1,545)
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Impaired loans	52,831		26,191
Provision for Credit Losses, Impaired Loans	(18,529)		(14,521)
Mortgage servicing rights	73,858		81,012
Mortgage Servicing Rights (MSR) Impairment (Recovery)	$ (121)		$ 545