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X-ray emission is one of the signposts of circumstellar interaction insupernovae (SNe), but until now, it has been observed only in core-collapseSNe. The level of thermal X-ray emission is a direct measure of the density ofthe circumstellar medium (CSM), and the absence of X-ray emission from Type IaSNe has been interpreted as a sign of a very low density CSM. In this paper, wereport late-time (500--800 days after discovery) X-ray detections of SN 2012cain {\it Chandra} data. The presence of hydrogen in the initial spectrum led toa classification of Type Ia-CSM, ostensibly making it the first SN~Ia detectedwith X-rays. Our analysis of the X-ray data favors an asymmetric medium, with ahigh-density component which supplies the X-ray emission. The data suggest anumber density $> 10^8$ cm$^{-3}$ in the higher-density medium, which isconsistent with the large observed Balmer decrement if it arises fromcollisional excitation. This is high compared to most core-collapse SNe, but itmay be consistent with densities suggested for some Type IIn or superluminousSNe. If SN 2012ca is a thermonuclear SN, the large CSM density could implyclumps in the wind, or a dense torus or disk, consistent with thesingle-degenerate channel. A remote possibility for a core-degenerate channelinvolves a white dwarf merging with the degenerate core of an asymptotic giantbranch star shortly before the explosion, leading to a common envelope aroundthe SN.

X-ray Emission from SN 2012ca: A Type Ia-CSM Supernova Explosion in a Dense Surrounding Medium