Subsequent Events (Details) $ / shares in Units, $ in Thousands			3 Months Ended	6 Months Ended
	Jul. 14, 2017 USD ($) bank $ / shares shares	Nov. 21, 2016 USD ($) shares	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2016 USD ($)	Dec. 31, 2016 USD ($)
Subsequent Event [Line Items]
Purchase of securities available for sale				$ 104,956	$ 96,873
Issuance of common stock related to acquisition				82,588
Assets				7,805,029		$ 7,211,611
Total loans				5,613,144		5,139,645
Deposits				6,017,104		$ 5,556,498
Subsequent event
Subsequent Event [Line Items]
Number of banking centers acquired | bank	122
IALB
Subsequent Event [Line Items]
Shares purchased (in shares) | shares		495,112
Percentage of interest acquired		12.10%
Purchase of securities available for sale		$ 19,800
Assets				1,100,000
Total loans				754,200
Deposits				$ 863,500
IALB | Subsequent event
Subsequent Event [Line Items]
Conversion of old shares	1.653
Issuance of common stock related to acquisition (in shares) | shares	6,000,000
Remeasurement loss			$ 50
Purchase price per share (usd per share) | $ / shares	$ 40.05
Issuance of common stock related to acquisition	$ 238,900