Business acquisition parking garage space of acquiree.

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Number of additional banking communities.

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Number of floors.

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Number of square feet.

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Percentage of occupancy.

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Percentage of occupancy including leased space.

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Percentage of property leased.

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Renovations cost.

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Date when the acquirer obtains control of the acquiree, in CCYY-MM-DD format.

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Recent Developments Including Mergers and Acquisitions - Additional Information (Detail) $ in Thousands					12 Months Ended
	Dec. 14, 2018 USD ($) ParkingSpaces	Aug. 31, 2018 USD ($) ft² Floor	Jan. 11, 2018 USD ($) Community Location	Jul. 31, 2017 shares	Dec. 31, 2017 USD ($)	Dec. 31, 2018 USD ($)
Business Combination Separately Recognized Transactions [Line Items]
Goodwill					$ 54,042	$ 79,749
Number of additional banking communities \| Community			5
Common Stock [Member]
Business Combination Separately Recognized Transactions [Line Items]
Stock split description					On July 31, 2017, the Company completed a two-for-one stock split of the Company’s outstanding shares of common stock.
Stock split conversion ratio				2
Stock payable in form of dividend, payable date				Jul. 31, 2017
Stock payable in form of dividend, record date				Jul. 17, 2017
Additional shares received by stockholders for each share held \| shares				1
First Bank & Trust Company [Member]
Business Combination Separately Recognized Transactions [Line Items]
Date of acquisition			Jan. 11, 2018
Total assets acquired			$ 290,000
Loans			247,000
Deposits			251,000
Intangibles assets, net			6,300
Goodwill			$ 19,100
First Bank of Chandler [Member]
Business Combination Separately Recognized Transactions [Line Items]
Date of acquisition			Jan. 11, 2018
Total assets acquired			$ 88,000
Loans			66,000
Deposits			79,000
Intangibles assets, net			2,200
Goodwill			$ 6,600
Number of locations acquired \| Location			2
BFTower LLC [Member] \| Cotter Ranch Tower [Member]
Business Combination Separately Recognized Transactions [Line Items]
Contract price		$ 21,000
Number of square feet \| ft²		507,000
Number of floors \| Floor		36
Date of acquisition		Aug. 31, 2018
Percentage of property leased		55.00%
Percentage of occupancy		35.00%
Percentage of occupancy including leased space		90.00%
Renovations period		2 years
Renovations cost		$ 60,000
BFTower LLC [Member] \| Cotter Ranch Tower [Member] \| SFPG, LLC [Member]
Business Combination Separately Recognized Transactions [Line Items]
Ownership interest acquired	42.60%
Space of parking garage \| ParkingSpaces	1,568
Payment to acquire ownership interest	$ 9,800