Acquisitions - Narrative (Details) $ / shares in Units, $ in Thousands		12 Months Ended
	Jul. 01, 2018 USD ($) $ / shares shares	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)
Business Acquisition [Line Items]
Goodwill		$ 808,322	$ 808,726
Grandpoint Capital, Inc.
Business Acquisition [Line Items]
Total assets acquired	$ 3,051,567	3,076,224
Gross loans acquired	2,400,000
Total deposits acquired	$ 2,506,663	2,506,929
Equity issued, ratio	0.4750
Consideration paid	$ 602,152
Aggregate cash consideration payable	$ 28,100
Company's common stock value (usd per share) | $ / shares	$ 38.15
Goodwill	$ 312,600	312,639
Net adjustment to loans, deferred tax assets and other assets since acquisition		$ 580
Grandpoint Capital, Inc. | Common Stock
Business Acquisition [Line Items]
Common stock issued as consideration (in shares) | shares	15,758,089