| Component: (Network and Table) | |
|---|---|
| Network | 00500 - Statement - Statements of Cash Flows (http://www.loxooncology.com/role/StatementStatementsOfCashFlows)  | 
| Table | (Implied) | 
| Reporting Entity [Axis] | 0001581720 (http://www.sec.gov/CIK) | 
| Statements of Cash Flows | Period [Axis] | ||
|---|---|---|---|
2016-01-01 - 2016-12-31  | 2015-01-01 - 2015-12-31  | 2014-01-01 - 2014-12-31  | |
Statements of Cash Flows  | |||
Operating activities:  | |||
Net loss  | (72,398,000)   | (35,876,000)   | (20,672,000)   | 
Adjustments to reconcile net loss to net cash used in operating activities:  | |||
Amortization of premium and discounts on investments  | |||
Depreciation of property and equipment  | |||
Stock-based compensation  | |||
Changes in operating assets and liabilities:  | |||
Prepaid expenses and other assets  | (  | (  | |
Accounts payable  | |||
Accrued expenses and other current liabilities  | |||
Net cash used in operating activities  | (  | (  | (  | 
Investing activities:  | |||
Purchases of available-for-sale securities  | (  | (  | (  | 
Proceeds from maturing available-for-sale securities  | |||
Purchase of property and equipment  | (  | (  | (  | 
Net cash used in investing activities  | (  | (  | (  | 
Financing activities:  | |||
Proceeds from issuance of redeemable convertible preferred stock, net  | |||
Proceeds from issuance of common stock, net  | |||
Proceeds from the exercise of stock options  | |||
Payment of deferred financing fees  | (  | ||
Net cash provided by financing activities  | |||
Net (decrease) increase in cash and cash equivalents  | (  | ||
Cash and cash equivalents-beginning of year  | 68,177,000    | ||
Cash and cash equivalents-end of year  | 30,376,000    | 68,177,000    | 43,930,000    | 
Supplemental schedule of noncash financing activities:  | |||
Conversion of redeemable convertible preferred stock into common stock  | |||
Reclassification of share repurchase obligation  | |||