Those who cannot consult Quran are idol worshipers because they fall for false authorities.
A person can be an idol worshiper regardless of the name of his religion.
God and His messenger command us not to marry an idol worshiper -
[2:221] Do not marry idolatresses unless they believe; a believing woman is better than an idolatress, even if you like her. Nor shall you give your daughters in marriage to idolatrous men, unless they believe. A believing man is better than an idolater, even if you like him. These invite to Hell, while GOD invites to Paradise and forgiveness, as He wills. He clarifies His revelations for the people, that they may take heed.
Who are idol worshipers anyway?
[16:35] The idol worshipers say, "Had GOD willed, we would not worship any idols besides Him, nor would our parents. Nor would we prohibit anything besides His prohibitions." Those before them have done the same. Can the messengers do anything but deliver the complete message?
Can a "Muslim" be idol worshiper? Absolutely yes! For example, the Quran warns very specifically against idolizing God's messengers and the saints. The Quran establishes the fact that no genuine messenger will ever command his people to glorify him or idolize him:
[3:79-80] Never would a human being whom God had blessed with the Scripture and prophethood say to the people "Idolize me besides God" but instead "devote yourself absolutely to your Lord alone" according to the Scripture you preach and the teachings you learn. Nor would he command you to idolize the angels and the prophets as Lords. Would he exhort you to disbelieve after becoming submitters ?
On the other hand, can a Hindu be believer? Absolutely yes! For example, if he believes in God, lead a righteous life and does not associate anyone with God.
"O friends, do not worship anybody but Him, the Divine One. Praise Him alone." [Rig Veda 8:1:1]
"I am the goal of life, the LORD and support of all, the inner witness, the abode of all. I am the only refuge, the ONE true friend; I am the beginning, the staying, and the end of creation; I am the womb and the eternal seed. I am heat; I give and withhold the rain. I am immortality and I am death; I am what is and what is not" [Bhagavad Gita 9:18-19]
"He is One only without a second." [Chandogya Upanishad 6:2:1]
"There is only one God, not the second; not at all, not at all, not in the least bit." [Brahma Sutra]
[2:62] Surely, those who believe, those who are Jewish, the Christians, and the converts; anyone who (1) believes in GOD, and (2) believes in the Last Day, and (3) leads a righteous life, will receive their recompense from their Lord. They have nothing to fear, nor will they grieve.
[5:69] Surely, those who believe, those who are Jewish, the converts, and the Christians; any of them who (1) believe in GOD and (2) believe in the Last Day, and (3) lead a righteous life, have nothing to fear, nor will they grieve.
Thank you and may God guide us