Mergers and Acquisitions Acquisition Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Business Acquisition [Line Items]
Labor and Related Expense	$ 49,965	$ 48,072	$ 37,220
Equipment And Software Expense	9,894	9,557	8,057
Occupancy, Net	6,884	7,088	5,695
Professional Fees	3,118	3,234	2,625
Other Noninterest Expense	10,948	10,687	9,210
Business Combination, Acquisition Related Costs	0	866	10,415
SBM Financial, Inc. [Member]
Business Acquisition [Line Items]
Labor and Related Expense	0	8
Equipment And Software Expense	0	279
Occupancy, Net	0	439
Professional Fees	0	80
Other Noninterest Expense	$ 0	$ 60
Business Acquisition One [Member]
Business Acquisition [Line Items]
Labor and Related Expense			3,240
Equipment And Software Expense			1,531
Occupancy, Net			1,237
Professional Fees			2,453
Other Noninterest Expense			$ 1,954