Leases (Narrative) (Details) - USD ($) $ in Thousands		3 Months Ended			9 Months Ended			12 Months Ended
		Sep. 30, 2019		Sep. 30, 2018	Sep. 30, 2019		Sep. 30, 2018	Dec. 31, 2018	Jan. 01, 2019
Operating lease right-of-use assets		$ 27,500			$ 27,500			$ 0	$ 28,900
Operating lease liabilities		$ 29,541	[1]		$ 29,541	[1]		$ 0	$ 30,900
Operating lease weighted average discount rate		3.66%			3.66%
Number of operating leases not yet commenced		1			1
Operating leases, weighted average lease term		14 years 1 month 6 days			14 years 1 month 6 days
Operating lease rent expense	[2]	$ 944		$ 942	$ 2,823		$ 2,800
Options to extend reasonably certain of being exercised					4,200
Short-term operating lease liabilities		$ 2,300			$ 2,300
Minimum [Member]
Lease expiration period					2 months			5 months
Operating lease renewal term		1 year			1 year
Lease expiration period, renewal option								1 year
Maximum [Member]
Lease expiration period					21 years			22 years
Operating lease renewal term		5 years			5 years
Lease expiration period, renewal option								5 years

[1] Includes short-term operating lease liabilities of $2.3 million.

[2] Included in net occupancy expenses in the Unaudited Consolidated Income Statement.