Acquisitions - Narrative (Details) $ in Thousands		6 Months Ended
	May 19, 2017 USD ($) bank shares	Jun. 30, 2017 USD ($) shares	Jun. 30, 2016 USD ($)
Business Acquisition [Line Items]
Issuance of common stock related to acquisition		$ 82,588
Common Stock
Business Acquisition [Line Items]
Stock issued as a part of acquisition (in shares) | shares		2,080,833
Issuance of common stock related to acquisition		$ 260
Arlington Bank
Business Acquisition [Line Items]
Percentage of interest acquired	100.00%
Number of banking centers acquired | bank	3
Stock issued as a part of acquisition (in shares) | shares	2,100,000
Issuance of common stock related to acquisition	$ 82,600
Core deposit intangible	$ 4,526
Acquired intangible asset, expected useful life	10 years
Arlington Bank | Common Stock
Business Acquisition [Line Items]
Number of shares of common stock	2.7245