Fixed TypeError and added documentation
diff --git a/docs/hazmat/primitives/cryptographic-hashes.rst b/docs/hazmat/primitives/cryptographic-hashes.rst
index 773d97f..43dee3f 100644
--- a/docs/hazmat/primitives/cryptographic-hashes.rst
+++ b/docs/hazmat/primitives/cryptographic-hashes.rst
@@ -54,6 +54,9 @@
:param bytes data: The bytes to be hashed.
:raises cryptography.exceptions.AlreadyFinalized: See :meth:`finalize`.
+ :raises TypeError: This exception is raised if ``data`` is not a binary
+ type. This is ``str`` in Python 2 and ``bytes`` in
+ Python 3.
.. method:: copy()