golden handshake

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun A lucrative severance agreement offered to an employee typically as an inducement to resign or retire.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun idiomatic A generous severance payment, especially as an inducement to leave employment.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a lucrative severance agreement offered to an employee (usually as an incentive to retire)