Mortgage servicer Nationstar Mortgage Holdings (NSM) maintains the distinction of being rated a high performing servicer by Fitch Ratings even as the company aggressively expands its portfolio of mortgage servicing rights.

The ratings giant affirmed Nationstar's subprime product at "RPS2" with outlook stable Tuesday and gave similar ratings to the Alt-A primary servicer product and the special servicer segment. Meanwhile, the master servicer rating came in at RMS2+. All of the company's servicing-related ratings came in as 'outlook stable.'

As for why Nationstar maintains high servicing ratings when it recently went on an MSR buying spree, Fitch says the servicer's rating also reflects the strength of the company's majority owner, Fortress Investment Co.  

Fitch also credits Nationstar's "effective default performance" and comprehensive servicing technology" for helping it maintain its stable ratings.  

The Lewisville, Texas-based company grew its primary and special servicing portfolio to 600,000 loans valued at $99.2 billion in June, up from 397,000 loans valued at $65.7 billion a year earlier. While a dramatic MSR portfolio increase was recently cited as a concern for Ocwen by Fitch, Nationstar's stable outlook remains in light of recent acquisitions.  

"Since Fitch's prior review, Nationstar completed its acquisition of Aurora's residential mortgage servicing platform and continues its integration of Aurora's servicing sites in Scottsbluff, Indianapolis, and Littleton," said Fitch. "The master servicing operation has remained in Littleton with the same management, staff, technology, and policies and procedures. Fitch views this positively as the master servicing operation was effective and well-managed prior to its acquisition by Nationstar."