Life insurance companies hold about $650 billion in commercial mortgages in the United States, yet little is known about their role as suppliers of real estate credit. Using regulatory data covering the universe of mortgage loans held by U.S. life insurers, we show that insurers complete this market, dominating long-maturity, low-leverage lending. We then show that aggregate macroeconomic shocks, specifically interest rates, transmit differently through insurers than through banks. When rates rise, banks cut lending and raise loan rates, while insurers expand lending and reduce loan spreads, without loosening collateral standards. Insurers' expansion is concentrated in shorter-maturity loans, a segment otherwise dominated by banks. We find that two reinforcing mechanisms explain insurers' response. Rising rates generate inflows into guaranteed-return products and narrow the duration gap embedded in insurers' long-dated liabilities, lowering the shadow cost of holding shorter-duration mortgage assets. At the same time, bank retrenchment shifts part of the residual borrower demand toward insurers. We isolate credit supply by exploiting cross-sectional variation in insurers' liability and asset durations, local exposure to bank retrenchment, and granular time-varying fixed effects. Our findings imply that bank-centered analyses may misstate the contraction in real estate credit when rates rise, and that monetary tightening reallocates credit not only across intermediaries, but also across maturities and borrowers.