Mergers and Acquisitions (Details)		12 Months Ended
	Oct. 16, 2015 USD ($) $ / shares shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($)	Sep. 14, 2016 $ / shares	Oct. 15, 2015
Business Acquisition [Line Items]
Equity interest issued		$ 0	$ 0	$ 110,551,000
Share Price | $ / shares					$ 31.75
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares | shares		3,450	9,450
Merger and acquisition costs		$ 0	$ 866,000	10,415,000
Goodwill		$ 94,697,000	94,697,000	95,657,000
Number of companies in integration		2
Payments of Stock Issuance Costs		$ 0	$ 0	$ 612,000
SBM Financial, Inc. [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	$ 86,785,000
Business acquisition, percentage of voting interest acquired	100.00%					80.00%
Business Acquisition, Cash Consideration, Per Share Amount | $ / shares	$ 206.00
Business Acquisition, Stock for Stock Consideration, Conversion Ratio	8.132
Total consideration paid	$ 136,676,000
Cash	$ 26,125,000
Business Acquisition, Equity Interest Issued or Issuable, Number of Shares | shares	4,124,643
Equity interest issued	$ 108,561,000
Share Price | $ / shares	$ 26.32
Share-based Compensation Arrangement by Share-based Payment Award, Options, Nonvested, Number of Shares | shares	139,032
Non-compete agreement costs		$ 400,000
Goodwill	$ 49,891,000
Loans and loans held for sale	$ 628,030,000
Nonqualified Stock Options [Member] | SBM Financial, Inc. [Member]
Business Acquisition [Line Items]
Business Acquisition, Stock for Stock Consideration, Conversion Ratio	8.132
Equity interest issued	$ 1,990,000
Scenario, Adjustment [Member] | SBM Financial, Inc. [Member]
Business Acquisition [Line Items]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	960,000
Loans and loans held for sale	$ 137,000