Consolidated Statements Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017
Cash flows from operating activities:
Net (loss) income	$ (2,958)	$ 19,567
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Amortization of deferred loan origination fees and costs	837	597
Net amortization of premiums and discounts on securities	707	687
Amortization on mortgage servicing rights	40	53
Amortization of debt issuance costs	312	27
Depreciation and amortization of office properties and equipment	1,834	1,849
Provision for loan losses	4,400	751
Gain on securities transactions, net	(116)	0
Gain on sale of loans receivable, net	15	170
Loss (gain) on real estate owned, net	13	(248)
Deferred tax expense (benefit)	6,811	(1,327)
Increase in accrued interest receivable	(1,152)	(341)
Increase in cash surrender value of bank-owned life insurance	2,127	2,105
Increase in other assets	(17,474)	(1,885)
Increase in accrued expenses and other liabilities	3,166	148
Contribution of common stock to Columbia Bank Foundation	34,767	0
Employee stock ownership plan expense	744	0
Net cash provided by operating activities	29,789	17,603
Cash flows from investing activities:
Proceeds from sales/calls of securities available-for-sale	9,966	0
Proceeds from principal pay downs / maturities on securities available-for-sale	29,541	35,828
Proceeds from principal pay downs / maturities on securities held-to-maturity	4,453	0
Purchases of securities available-for-sale	(278,610)	(28,947)
Purchases of securities held-to-maturity	(19,761)	0
Proceeds from sales of loans receivable	3,695	31,237
Purchases of loan receivables	(4,715)	(7,358)
Loan originations, net of principal payments	(252,786)	(243,759)
Proceeds from bank-owned life insurance	811	977
Proceeds from sales of Federal Home Loan Bank stock	40,226	16,983
Purchases of Federal Home Loan Bank stock	(40,571)	(20,649)
Additions to office properties and equipment	(5,837)	(4,013)
Proceeds from sales of real estate owned	286	1,186
Net cash used in investing activities	(513,302)	(218,515)
Cash flows from financing activities:
Net increase in deposits	31,517	131,730
Proceeds from long-term borrowings	184,049	161,200
Payments for maturities, calls, and payoffs on borrowings	(7,399,600)	(3,161,950)
Increase in short-term borrowings	7,216,800	3,079,450
Increase in advance payments by borrowers for taxes and insurance	5,432	3,836
Issuance of common stock	492,428	0
Purchase of employee stock ownership plan shares	(45,428)	0
Net cash provided by financing activities	485,198	214,266
Net increase in cash and cash equivalents	1,685	13,354
Cash and cash equivalents at beginning of year	65,498	40,561
Cash and cash equivalents at end of period	67,183	53,915
Cash paid during the period for:
Interest	26,947	21,833
Income tax payments, net	9,435	15,903
Non-cash investing and financing activities:
Transfer of loans receivable to real estate owned	$ 0	$ 538