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, 2018	Mar. 31, 2017	Dec. 31, 2017
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Commercial Loans Held-for-sale, Fair Value Disclosure	$ 6,091		$ 0
Mortgage servicing rights	66,407		58,384
Mortgage Servicing Rights (MSR) Impairment (Recovery)	(474)	$ 217
Fair Value, Inputs, Level 2
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Commercial Loans Held-for-sale, Fair Value Disclosure	6,091		0
Residential Held-for-sale, Fair Value Disclosure	103,953		85,544
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 2
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Commercial Loans Held-for-sale, Fair Value Disclosure	6,091
Provision for Credit Losses, Commercial Loans held-for-sale	0
Other Real Estate Owned Fair Value Disclosure	2,088		2,604
Foreclosure / OREO expense, net	(553)		(939)
Fair Value, Measurements, Nonrecurring [Member] | Fair Value, Inputs, Level 3
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Impaired loans	74,038		92,534
Provision for Credit Losses, Impaired Loans	14,518		32,159
Mortgage servicing rights	81,810		64,387
Mortgage Servicing Rights (MSR) Impairment (Recovery)	$ 474		$ (175)