Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Cash flows from operating activities:
Net income	$ 142,048	$ 71,274	$ 93,606
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit loss expense (release)	8,295	36,729	(9,293)
Depreciation and amortization	23,853	16,448	13,585
Change in current income tax receivable	3,223	(3,880)	1,045
Change in deferred income taxes	55	(17,280)	(226)
Discount accretion, net of premium amortization on securities	(831)	1,111	4,335
Gain on sale of mortgages, net	(9,907)	(19,747)	(56,946)
Origination of loans held for sale, net of repayments	(398,438)	(810,061)	(1,867,734)
Proceeds from sales of loans held for sale	407,425	955,044	2,041,158
Originations of mortgage servicing rights	(1,183)	(4,187)	(7,882)
Proceeds from sales of mortgage servicing rights	5,502		11,375
Gain on sale of mortgage servicing rights	(1,052)		(1,290)
Impairment on fixed assets	349	118	1,553
Gain on sale of fixed assets	(148)	(1,674)	(3,768)
Gain from banking center divestiture			(778)
Stock-based compensation	7,222	6,059	5,541
Operating lease payments	(6,308)	(5,036)	(5,099)
Change in other assets	343	(26,749)	11,390
Change in other liabilities	(13,513)	16,465	(51,070)
Net cash provided by operating activities	166,935	214,634	179,502
Cash flows from investing activities:
Proceeds from non-marketable securities	100,046	4,175	2,006
Proceeds from maturities of investment securities available-for-sale	92,032	141,892	235,860
Proceeds from maturities of investment securities held-to-maturity	69,555	133,363	161,923
Proceeds from sales of investment securities available-for-sale		128,430
Proceeds from sales of other real estate owned	581	3,564	1,917
Purchase of non-marketable securities	(106,175)	(37,271)	(27,688)
Purchase of investment securities available-for-sale	0	(259,846)	(288,580)
Purchase of investment securities held-to-maturity	(2,452)	(101,699)	(397,758)
(Purchases) sales of premises and equipment, net	(36,834)	(12,430)	5,146
Net increase in loans	(477,109)	(987,511)	(166,662)
Proceeds from the sale of loans	1,625	933
Net cash activity from acquisition	(45,300)	234,263
Net cash used in investing activities	(404,031)	(752,137)	(473,836)
Cash flows from financing activities:
Net increase (decrease) in deposits	317,050	(465,818)	552,719
Net decrease in repurchase agreements and other short-term borrowings	(587)	(2,554)	(129)
Proceeds from long-term debt			40,000
Payment of long-term debt issuance costs			(535)
Advances from the Federal Home Loan Bank	4,256,490	570,500
Federal Home Loan Bank repayments	(4,301,490)	(185,500)
Issuance of stock under purchase and equity compensation plans	(1,534)	(1,481)	(2,267)
Proceeds from exercise of stock options	617	1,102	2,489
Payment of dividends	(39,643)	(30,447)	(26,888)
Repurchase of common stock			(36,400)
Net cash provided by (used in) financing activities	230,903	(114,198)	528,989
(Decrease) increase in cash, cash equivalents and restricted cash(1)	(6,193)	(651,701)	234,655
Cash, cash equivalents and restricted cash at beginning of the year(1)	198,519	850,220	615,565
Cash, cash equivalents and restricted cash at end of period(1)	192,326	198,519	850,220
Supplemental disclosure of cash flow information during the period:
Cash paid for interest	124,426	18,597	16,638
Net tax payments	32,846	11,302	15,389
Supplemental schedule of non-cash activities:
Loans transferred from loans held for sale to loans	4,833	5,288	$ 7,807
Rock Canyon Bank
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit loss expense (release)	5,400
Supplemental schedule of non-cash activities:
Treasury stock reissued for acquisition		60,642
Bank of Jackson Hole
Adjustments to reconcile net income to net cash provided by operating activities:
Provision for credit loss expense (release)	$ 16,300
Supplemental schedule of non-cash activities:
Treasury stock reissued for acquisition		$ 84,122