Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Cash flows from operating activities:
Net loss	$ (10,134)	$ (10,183)
Adjustments to reconcile net loss to net cash used in operating activities:
Share-based compensation expense	3,890	3,628
Depreciation	1,857	1,962
Amortization of intangible assets	342	342
Amortization of deferred financing costs	93	66
(Gain) loss on disposal of property and equipment	(5)	62
Realized (gain) loss from foreign exchange on intercompany transactions	(82)	21
(Accretion) amortization of investments	(15)	38
Change in allowance for doubtful accounts	51	(136)
Changes in operating assets and liabilities:
Accounts receivable	783	(397)
Inventories	(43)	(1,145)
Other current assets	(1,540)	(1,175)
Accounts payable	(408)	353
Accrued liabilities	(4,244)	(2,827)
Other noncurrent assets and liabilities	21	(155)
Net cash used in operating activities	(9,434)	(9,546)
Cash flows from investing activities:
Purchases of available-for-sale securities	(10,359)	(3,096)
Sales and maturities of available-for-sale securities	8,200	10,550
Purchases of property and equipment	(2,086)	(1,728)
Net cash (used in) provided by investing activities	(4,245)	5,726
Cash flows from financing activities:
Proceeds from debt borrowings	17,381
Payments on debt and capital leases	(1,326)	(120)
Payment of debt fees	(1,114)
Proceeds from stock option exercises	1,787	631
Shares repurchased for payment of taxes on stock awards	(3,665)	(1,735)
Net cash provided by (used in) financing activities	13,063	(1,224)
Effect of exchange rate changes on cash and cash equivalents	36	(10)
Net decrease in cash and cash equivalents	(580)	(5,054)
Cash and cash equivalents-beginning of period	21,809	24,208
Cash and cash equivalents-end of period	21,229	19,154
Supplemental cash flow information:
Cash paid for interest	416	488
Cash paid for income taxes
Non-cash investing and financing activities:
Accrued purchases of property and equipment	178	559
Assets acquired through capital lease	27
Capital lease asset early termination	$ (9)

Capital lease asset early termination.

No definition available.

Name:	atrc_CapitalLeaseAssetEarlyTermination
Namespace Prefix:	atrc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The sum of the periodic adjustments of the differences between securities' face values and purchase prices that are charged against earnings. This is called accretion if the security was purchased at a discount and amortization if it was purchased at premium. As a noncash item, this element is an adjustment to net income when calculating cash provided by or used in operations using the indirect method.