Subsequent Events	9 Months Ended
	Sep. 30, 2021
Subsequent Events [Abstract]
Subsequent Events	Subsequent EventsOn October 1, 2021, the Company acquired 100% percent of the outstanding common stock of Altabancorp and its wholly-owned subsidiary, Altabank, a community bank based in American Fork, Utah (collectively, “Alta”). Alta provides banking services to individuals and businesses in Utah with twenty-five banking offices from Preston, Idaho to St. George, Utah. The acquisition expanded the Company’s presence in Utah. As of September 30, 2021, Altabancorp had total assets of $3,647,728,000, gross loans of $1,901,181,000, and total deposits of $3,278,907,000. The preliminary value of the Alta acquisition is $839,852,000 and resulted in the Company issuing 15,173,480 shares of its common stock. The fair value of the Company shares issued was determined on the basis of the opening market price of the Company’s common stock on the October 1, 2021 acquisition date. The excess of the fair value of consideration transferred over total identifiable net assets will be recorded as goodwill. The initial accounting for the acquisition has not been completed because the information to measure the fair value of financial assets, financial liabilities and goodwill is not yet available. The Company expects to finalize the valuation and complete the purchase price allocation as soon as practicable, but no later than one year from the acquisition date.