Loan Servicing Rights - LSRs Activity (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017	[1]	Dec. 31, 2016	[2]
Loan Servicing Rights
Cumulative effect adjustment of change in accounting policy, net of tax impact			$ 1,339		$ 3,659
Activity for loan servicing rights and the related fair value changes
Fair value, beginning of period	$ 63,841	$ 48,085
Transfers in based on new accounting policy election(2)		15,891
Additions from loans sold with servicing retained	1,967	1,753
Changes in fair value due to:
Reductions from pay-offs, pay downs and run-off	723	606
Changes in estimates of fair value	3,752	(519)
Fair value, end of period	68,837	64,604
Principal balance of loans serviced for others that have servicing capitalized	7,060,339	7,304,338
Commercial Real Estate
Activity for loan servicing rights and the related fair value changes
Fair value, beginning of period	427	344
Transfers in based on new accounting policy election(2)		0
Additions from loans sold with servicing retained	43	0
Changes in fair value due to:
Reductions from pay-offs, pay downs and run-off	(29)	(24)
Changes in estimates of fair value	0	0
Fair value, end of period	441	320
Principal balance of loans serviced for others that have servicing capitalized	42,032	50,942
Mortgage
Activity for loan servicing rights and the related fair value changes
Fair value, beginning of period	63,414	47,741
Transfers in based on new accounting policy election(2)		15,891
Additions from loans sold with servicing retained	1,924	1,753
Changes in fair value due to:
Reductions from pay-offs, pay downs and run-off	(694)	(582)
Changes in estimates of fair value	3,752	(519)
Fair value, end of period	68,396	64,284
Principal balance of loans serviced for others that have servicing capitalized	$ 7,018,307	$ 7,253,396
Retained earnings
Loan Servicing Rights
Cumulative effect adjustment of change in accounting policy, net of tax impact			$ 1,680		$ 3,659

[1] Refer to Note 1, Basis of Presentation and Significant Accounting Policies, Note 3, Investment Securities, Note 5, Other Real Estate Owned and Repossessed Assets and Note 9, Derivative Instruments and Balance Sheet Offsetting, for further details on the changes in accounting policy.

[2] Refer to Note 1, Basis of Presentation and Significant Accounting Policies and Note 7, Loan Servicing Rights for further details on the changes in accounting policy.