Fair Value of Financial Instruments - Nonrecurring Assets Measured at Fair Value (Details) - Nonrecurring - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Assets Measured at Fair Value on Non Recurring Basis
Impaired loans	$ 23,257	$ 15,550
ORE, net	4,993	3,223
Residential mortgage servicing rights	57,895	44,600
SBA servicing rights	1,027
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets Measured at Fair Value on Non Recurring Basis
Impaired loans	0	0
ORE, net	0	0
Residential mortgage servicing rights	0	0
SBA servicing rights	0
Significant Other Observable Inputs (Level 2)
Assets Measured at Fair Value on Non Recurring Basis
Impaired loans	0	0
ORE, net	0	0
Residential mortgage servicing rights	0	0
SBA servicing rights	0
Significant Unobservable Inputs (Level 3)
Assets Measured at Fair Value on Non Recurring Basis
Impaired loans	23,257	15,550
ORE, net	4,993	3,223
Residential mortgage servicing rights	57,895	$ 44,600
SBA servicing rights	$ 1,027