Fair Value Measurements, Assets and Liabilities Measured at Fair Value on a Nonrecurring Basis (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Mortgage servicing rights	$ 58,384	$ 61,476	$ 61,341
Mortgage Servicing Rights (MSR) Impairment (Recovery)	175	(200)	$ (425)
Fair Value, Inputs, Level 2
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Commercial loans held for sale	0	12,474
Mortgage loans held for sale	85,544	108,010
Fair Value, Measurements, Nonrecurring | Fair Value, Inputs, Level 2
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Commercial loans held for sale		12,474
Provision for credit losses		(559)
Mortgage loans held for sale		108,010
Market valuation adjustment, mortgage loans held for sale		(3,760)
Other real estate owned	2,604	9,752
Foreclosure / OREO expense, net	(939)	(1,091)
Fair Value, Measurements, Nonrecurring | Fair Value, Inputs, Level 3
Assets and Liabilities Measured at Fair Value on a Non-recurring Basis
Impaired loans	92,534	79,270
Provision for Credit Losses, Impaired Loans	(32,159)	(75,194)
Mortgage servicing rights	64,387	73,149
Mortgage Servicing Rights (MSR) Impairment (Recovery)	$ (175)	$ 200