Leases - Operating Leases for Premises and Equipment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Rental expense, net of sublease income
Net rental expense	$ 7,563	$ 7,712	$ 7,493
Future minimum Operating Lease Payments
2018	7,694
2019	7,449
2020	6,823
2021	5,184
2022	2,557
Thereafter	18,004
Total	47,711
Future minimum Operating Lease Payments, Sublease Income
2018	893
2019	893
2020	893
2021	881
Total	3,560
Future minimum Operating Lease Payments, Net Lease Payments
2018	6,801
2019	6,556
2020	5,930
2021	4,303
2022	2,557
Thereafter	18,004
Total	$ 44,151
Maximum
Leases for premises and equipment
Lease terms, including renewal options	46 years
Occupancy
Rental expense, net of sublease income
Rental expense charged to occupancy	$ 8,620	8,689	8,698
Less: sublease income	1,342	1,303	1,588
Net rental expense	7,278	7,386	7,110
Equipment
Rental expense, net of sublease income
Rental expense charged to equipment expense	$ 285	$ 326	$ 383