Collins Chinese Dictionary Plus (3rd edition), 2011:
理所当(當)然 lǐ suǒ dāng rán natural
- 他认(認)为(為)我给(給)他礼(禮)物是理所当(當)然的。 Tā rènwéi wǒ gěi tā lǐwù shì lǐ suǒ dāng rán de. He reckons it's entirely natural that I should give him a present.