Marc Nachmann, Goldman Sachs global head of asset and wealth management.

CNBC

Goldman Sachs said Thursday it won deals to manage a combined $70 billion in retirement assets for Verizon Communications and Lockheed Martin, one of the larger recent announcements in the fast-growing market for outsourced corporate investing.

The mandates include about $30 billion in pension assets for Verizon and Lockheed Martin and $40 billion in Verizon defined-contribution retirement assets, which are typically 401(k)s, according to Goldman.

The moves underscore how some of America's largest employers are increasingly handing responsibility for managing retirement assets to outside firms like Goldman as portfolios become more complex and require expertise across public and private markets.

Competition in the multitrillion-dollar market for retirement assets is fierce among managers including Goldman, BlackRock, Russell Investments and Mercer, because the long-term institutional mandates generate steady fee revenue.

By growing that business, Goldman hopes to increase its share of revenues that are seen as stable and recurring, unlike the more volatile trading and investment banking operations.

"Large plan sponsors are consolidating responsibilities with one partner with the investment expertise and depth of platform to manage their bespoke needs," Marc Nachmann, Goldman's global head of asset and wealth management, said in a statement.

Goldman's outsourced chief investment officer business had about $480 billion in assets as of March 31, while the firm's broader asset and wealth management division oversees roughly $3.7 trillion worth of investments.