Loans and Leases - Loan Mark (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Loans and Leases Receivable Disclosure [Line Items]
Acquired loans, outstanding principal	$ 507,085	$ 559,815
Acquired loans, remaining loan mark	(15,841)	(17,912)
Acquired loans, recorded investment	491,244	541,903
Commercial mortgage
Loans and Leases Receivable Disclosure [Line Items]
Acquired loans, outstanding principal	318,488	339,241
Acquired loans, remaining loan mark	(8,404)	(9,627)
Acquired loans, recorded investment	310,084	329,614
Home equity loans and lines
Loans and Leases Receivable Disclosure [Line Items]
Acquired loans, outstanding principal	26,981	28,212
Acquired loans, remaining loan mark	(2,265)	(2,367)
Acquired loans, recorded investment	24,716	25,845
Residential mortgage
Loans and Leases Receivable Disclosure [Line Items]
Acquired loans, outstanding principal	81,372	86,111
Acquired loans, remaining loan mark	(2,631)	(2,778)
Acquired loans, recorded investment	78,741	83,333
Construction
Loans and Leases Receivable Disclosure [Line Items]
Acquired loans, outstanding principal	2,190	6,780
Acquired loans, remaining loan mark	(1)	(294)
Acquired loans, recorded investment	2,189	6,486
Commercial and industrial
Loans and Leases Receivable Disclosure [Line Items]
Acquired loans, outstanding principal	56,400	72,948
Acquired loans, remaining loan mark	(1,903)	(2,007)
Acquired loans, recorded investment	54,497	70,941
Consumer
Loans and Leases Receivable Disclosure [Line Items]
Acquired loans, outstanding principal	2,680	2,828
Acquired loans, remaining loan mark	(88)	(113)
Acquired loans, recorded investment	2,592	2,715
Leases
Loans and Leases Receivable Disclosure [Line Items]
Acquired loans, outstanding principal	18,974	23,695
Acquired loans, remaining loan mark	(549)	(726)
Acquired loans, recorded investment	$ 18,425	$ 22,969