Willis Group Holdings Plc’s agreement to merge with Towers Watson & Co. could provide CEO Dominic Casserley with a golden parachute of almost $18 million.

Casserley is eligible for the payment when he resigns as CEO of Willis because he’s not the most senior executive at the combined company, according to the terms of his employment agreement in Willis’s April 17 proxy filing. The package was valued at $17.7 million as of the company’s Dec. 31 fiscal-year end and includes $8.2 million in cash severance and $9.5 million in early equity vesting, according to the filing.

Casserley will resign as CEO of Willis and be appointed deputy CEO of the combined company, according to the merger agreement, while Towers CEO John J. Haley will lead the combined company. Willis, the third-largest insurance broker, agreed to merge with Towers Watson in a deal valued at about $8.7 billion to take on larger rivals and add consulting operations.

“It doesn’t look like it’s a transaction that benefits him personally in any unique way, besides for the golden parachute,” said Paul Newsome, an analyst at Sandler O’Neill & Partners. “It may be that what people remember him for is merging with Towers.”

The transaction will create tax advantages for the combined company, which will be domiciled in Ireland. Miles Russell, a spokesman for Willis, declined to comment on Casserley’s payment.

Casserley joined the firm in 2013 after working at McKinsey & Co. for almost 30 years, Willis said at the time of his hiring.

Willis’s board asked Casserley to perform a strategic review when he came to the company, he said on a Tuesday conference call with analysts discussing the deal. He’s pursued transactions to expand the company, including an April offer to buy the 70 percent of French broker Gras Savoye SAS that it didn’t already own and an agreement this year to purchase Miller Insurance Services.