Moody's affirmed Nationstar Mortgage LLC's B2 senior unsecured debt and corporate family ratings with a stable outlook.

The rating agency cited as reasons for the B2 ratings Nationstar's position in the U.S. residential mortgage servicing market, constrained profitability and moderate financial leverage, along with the rapid growth of its servicing portfolio, mitigated by the company's track record of buying and integrating residential mortgage servicing assets.

Moody's said the outlook reflects its expectation that the company will keep its solid servicing performance and see financial benefits from its larger servicing portfolio. The agency also expects the company's profitability to improve as a result of rising interest rates. Core profitability is expected to improve modestly during 2017, and the company is expected to maintain its leverage, particularly on a risk-weighted basis, Moody's said.