CONDENSED CONSOLIDATED STATEMENTS OF CASH FLOWS (UNAUDITED) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024
Cash flows from operating activities
Net income attributable to BlackLine, Inc.	$ 14,347	$ 87,519
Net income and adjustment attributable to redeemable non-controlling interest (Note 4)	(1,682)	2,210
Net income	12,665	89,729
Adjustments to reconcile net income to net cash provided by operating activities:
Depreciation and amortization	22,973	25,300
Amortization of debt issuance costs	1,679	2,679
Stock-based compensation	43,231	41,288
Gain on extinguishment of convertible senior notes	0	(65,112)
Noncash lease expense	2,694	3,110
Accretion of purchase discounts on marketable securities, net	(5,361)	(15,261)
Net foreign currency (gains) losses	561	(157)
Deferred income taxes	(2,234)	(1,255)
Provision for credit losses	75	7
Changes in operating assets and liabilities:
Accounts receivable	5,468	33,995
Prepaid expenses and other current assets	4,788	3,524
Other assets	(1,428)	1,609
Accounts payable	2,529	(6,543)
Accrued expenses and other current liabilities	(12,989)	(10,896)
Deferred revenue	2,248	(7,802)
Operating lease liabilities	(3,239)	(3,241)
Lease incentive receipts	30	0
Other long-term liabilities	5,397	149
Net cash provided by operating activities	79,087	91,123
Cash flows from investing activities
Purchases of marketable securities	(476,940)	(396,104)
Proceeds from maturities of marketable securities	84,000	591,500
Proceeds from sales of marketable securities	0	324,098
Capitalized software development costs	(14,161)	(12,087)
Purchases of property and equipment	(6,917)	(976)
Net cash provided by (used in) investing activities	(414,018)	506,431
Cash flows from financing activities
Proceeds from issuance of convertible senior notes, net of issuance costs	0	662,641
Partial repurchase of convertible senior notes	0	(848,519)
Purchase of capped calls related to convertible senior notes	0	(59,738)
Principal payments under finance lease obligations	(60)	(516)
Repurchases of common stock	(88,783)	0
Proceeds from exercises of stock options	5,018	2,638
Proceeds from employee stock purchase plan	4,592	4,249
Acquisition of common stock for tax withholding obligations	(12,991)	(12,384)
Net cash used in financing activities	(92,224)	(251,629)
Effect of foreign currency exchange rate changes on cash, cash equivalents, and restricted cash	410	(421)
Net increase (decrease) in cash, cash equivalents, and restricted cash	(426,745)	345,504
Cash, cash equivalents, and restricted cash, beginning of period	886,147	271,363
Cash, cash equivalents, and restricted cash, end of period	459,402	616,867
Reconciliation of cash, cash equivalents, and restricted cash to the condensed consolidated balance sheets
Cash and cash equivalents at end of period	459,141	616,629
Restricted cash included within other assets at end of period	261	238
Total cash, cash equivalents, and restricted cash at end of period shown in the condensed consolidated statements of cash flows	459,402	616,867
Non-cash financing and investing activities
Stock-based compensation capitalized for software development	2,251	2,079
Capitalized software development costs included in accounts payable and accrued expenses and other current liabilities at end of period	1,343	1,166
Purchases of property and equipment included in accounts payable and accrued expenses and other current liabilities at end of period	505	140
Excise tax on repurchases of common stock	485	0
Debt issuance costs included in accounts payable and accrued expenses at end of period	$ 0	$ 663