Income Taxes, Effective Income Tax Rate Reconciliation (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Tax Provision at Federal Statutory Rate									$ 19,068	$ 16,037	$ 15,510
Interest on Obligations of States and Political Subdivisions exempt from Federal Taxation									(617)	(675)	(711)
State and Local Income Taxes, Net of Federal Income Tax Benefit									3,573	2,992	2,966
Bank Owned Life Insurance									(696)	(731)	(712)
Low-Income Housing Tax Credit									(1,546)	(1,201)	(291)
Bargain Purchase Gain									0	(641)	0
Deferred Tax Asset Remeasurement									6,256	0	0
Other, Net									73	316	162
Total Provision for Taxes	$ 11,974	$ 5,000	$ 4,708	$ 4,429	$ 3,389	$ 4,503	$ 4,169	$ 4,036	$ 26,111	$ 16,097	$ 16,924
Effective Income Tax Rate Reconciliation, Percent [Abstract]
Tax Provision at Federal Statutory Rate									35.00%	35.00%	35.00%
Interest on Obligations of States and Political Subdivisions exempt from Federal Taxation									(1.10%)	(1.50%)	(1.60%)
State and Local Income Taxes, Net of Federal Income Tax Benefit									6.50%	6.50%	6.70%
Bank Owned Life Insurance									(1.30%)	(1.60%)	(1.60%)
Low-Income Housing Tax Credit									(2.80%)	(2.60%)	(0.70%)
Bargain Purchase Gain									(0.00%)	(1.40%)	(0.00%)
Deferred Tax Asset Remeasurement									11.50%	0.00%	0.00%
Other, Net									0.10%	0.70%	0.40%
Total Provision for Taxes									47.90%	35.10%	38.20%