Assets under contract totaled $987 billion, and assets under management were $113.4 billion. Asset enrollment rates across all employer plans was 11.5 percent.

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In the fourth quarter alone, $1.9 billion in contributions were made to managed accounts and $4.3 billion in assets came from new enrollees in managed accounts.

Managed account revenue accounts for most of the company's revenue.

The firm's acquisition of The Mutual Fund Store closed on February 1. The move was announced last year and will allow participants in 401(k) plans provided by Financial Engines to have access to face-to-face advice at any of The Mutual Fund Store's 129 locations across the country.

Despite the fact that Financial Engines is regarded as a robo-advisor by some in the industry, its push to add a human touch through the acquisition came after it opened direct access for all participants to its live stable of investment advisors.

Before access was broadened, only participants in its managed accounts—approximately 500,000—had that option.

At the time the acquisition was announced, Lawrence Raffone, president and chief executive officer of Financial Engines, said the added human advisory capability would help participants better manage their complete financial picture.

In the announcement of last year's results, Raffone commented again on the acquisition in a statement. He said, "During 2015, we achieved solid results and took meaningful steps with the acquisition of The Mutual Fund Store that we believe will strengthen our business and drive sustained future growth. We are excited about the capabilities and programs we will be adding to enhance our services and see a huge opportunity to help more workplace participants achieve greater financial security."

"We anticipate acceleration to our growth with the integration of The Mutual Fund Store's core strengths," Ray Sims, chief financial officer of Financial Engines, said in a statement. "Post-closing, we remain debt free and expect to generate significant cash flow that will enable us to continue to invest in the business and drive our growth."