diff --git a/docs/hazmat/primitives/symmetric-encryption.rst b/docs/hazmat/primitives/symmetric-encryption.rst
index 2ee5085..daa4b36 100644
--- a/docs/hazmat/primitives/symmetric-encryption.rst
+++ b/docs/hazmat/primitives/symmetric-encryption.rst
@@ -165,6 +165,16 @@
         >>> decryptor.update(ct)
         'a secret message'
 
+.. class:: IDEA(key)
+
+    IDEA (`International Data Encryption Algorithm`_) is a block cipher created
+    in 1991. It is an optional component of the `OpenPGP`_ standard. This cipher
+    is susceptible to attacks when using weak keys. It is recommended that you
+    do not use this cipher for new applications.
+
+    :param bytes key: The secret key, 128 bits in length.  This must be kept
+                      secret.
+
 
 .. _symmetric-encryption-modes:
 
@@ -468,3 +478,5 @@
 .. _`encrypt`: https://ssd.eff.org/tech/encryption
 .. _`CRYPTREC`: http://www.cryptrec.go.jp/english/
 .. _`significant patterns in the output`: http://en.wikipedia.org/wiki/Cipher_block_chaining#Electronic_codebook_.28ECB.29
+.. _`International Data Encryption Algorithm`: https://en.wikipedia.org/wiki/International_Data_Encryption_Algorithm
+.. _`OpenPGP`: http://www.openpgp.org