Mortgage Servicing Rights - Loans, Fees, Amortization and Carrying Value (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Other Intangible Assets
Unpaid principal amount of consumer loans serviced for others	$ 2,500,000		$ 2,500,000		$ 2,700,000
Contractually specified fees, late charges, and ancillary fees	1,600	$ 1,900	3,200	$ 3,600
Amortization of mortgage servicing rights	842	1,020	1,606	$ 2,008
MSRs
Other Intangible Assets
Amortization of mortgage servicing rights	800	$ 1,000
Estimated future amortization expenses
Under one year	2,254		2,254
One to two years	1,950		1,950
Two to three years	1,687		1,687
Three to four years	1,463		1,463
Four to five years	1,269		1,269
Details of mortgage servicing rights
Gross carrying amount	63,366		63,366		63,342
Less: accumulated amortization	48,793		48,793		47,187
Net carrying value	$ 14,573		$ 14,573		$ 16,155