Consolidated Statements Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
Cash flows from operating activities:
Net income	$ 7,869	$ 21,080
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred loan origination fees and costs	1,420	945
Net amortization of premiums and discounts on securities	1,017	1,294
Amortization on mortgage servicing rights	57	76
Amortization of debt issuance costs	890	40
Depreciation and amortization of office properties and equipment	2,748	2,686
Provision for loan losses	5,900	6,426
(Gain) Loss on securities transactions, net	(116)	2,099
(Gain) Loss on sale of loans receivable, net	(15)	789
Loss (gain) on real estate owned, net	45	(245)
Gain on disposal of office properties and equipment	0	(14)
Deferred tax expense	6,764	11,482
Increase in accrued interest receivable	(2,679)	(629)
Increase in cash surrender value of bank-owned life insurance	(3,435)	(3,196)
Increase in other assets	(13,801)	(14,955)
Increase (decrease) in accrued expenses and other liabilities	3,505	(1,496)
Contribution of common stock to Columbia Bank Foundation	34,767	0
Employee stock ownership plan expense	1,700	0
Net cash provided by operating activities	46,636	26,382
Cash flows from investing activities:
Proceeds from sales/calls of securities available-for-sale	11,513	129,335
Proceeds from principal pay downs / maturities on securities available-for-sale	49,446	51,411
Proceeds from principal pay downs / maturities on securities held-to-maturity	6,846	769
Purchases of securities available-for-sale	(361,263)	(149,506)
Purchases of securities held-to-maturity	(31,639)	(30,484)
Proceeds from sales of loans receivable	3,695	77,776
Purchases of loan receivables	(4,715)	(11,059)
Loan originations, net of principal payments	(451,223)	(291,173)
Purchase of bank-owned life insurance	(30,000)	(4,500)
Proceeds from bank-owned life insurance	811	977
Proceeds from sales of Federal Home Loan Bank stock	51,676	24,351
Purchases of Federal Home Loan Bank stock	(63,544)	(23,862)
Proceeds from sales of office properties and equipment	0	17
Additions to office properties and equipment	(8,799)	(5,607)
Proceeds from sales of real estate owned	914	1,278
Net cash used in investing activities	(826,282)	(230,277)
Cash flows from financing activities:
Net increase in deposits	109,030	251,930
Proceeds from long-term borrowings	180,130	148,400
Payments for maturities, calls, and payoffs on borrowings	(17,478,700)	(4,777,450)
Increase in short-term borrowings	17,555,900	4,638,250
Payment for trust preferred securities	(51,547)	0
Increase in advance payments by borrowers for taxes and insurance	7,169	3,179
Issuance of common stock	492,428	0
Purchase of employee stock ownership plan shares	(45,428)	0
Net cash provided by financing activities	768,982	264,309
Net (decrease) increase in cash and cash equivalents	(10,664)	60,414
Cash and cash equivalents at beginning of year	65,498	40,561
Cash and cash equivalents at end of period	54,834	100,975
Cash paid during the period for:
Interest	45,306	34,575
Income tax payments, net	13,435	21,302
Non-cash investing and financing activities:
Transfer of loans receivable to real estate owned	251	538
Transfer of loans to held-for-sale from loans receivable	1,860	0
Transfer of securities from available-for-sale to held-to-maturity	$ 0	$ 103,680