Mortgage Servicing Rights - Loans, Fees, Amortization and Carrying Value (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Other Intangible Assets
Unpaid principal amount of consumer loans serviced for others	$ 2,400,000		$ 2,400,000		$ 2,700,000
Contractually specified fees, late charges, and ancillary fees	1,600	$ 1,700	4,800	$ 5,300
Amortization of mortgage servicing rights	978	956	2,584	$ 2,965
MSRs
Other Intangible Assets
Amortization of mortgage servicing rights	1,000	$ 1,000
Estimated future amortization expenses
Under one year	2,467		2,467
One to two years	2,048		2,048
Two to three years	1,693		1,693
Three to four years	1,403		1,403
Four to five years	1,172		1,172
Details of mortgage servicing rights
Gross carrying amount	63,401		63,401		63,342
Less: accumulated amortization	49,771		49,771		47,187
Net carrying value	$ 13,630		$ 13,630		$ 16,155