Squeezed states of light are a key resource for quantum information, and the detection of squeezing is vital in experimental quantum optics. Although squeezed vacuum can be generated at bandwidths of 10 THz and more by broadband parametric down conversion, the bandwidth of standard squeezing detection methods is limited by the photo-detectors to several GHz at most. We propose sum-frequency generation as a physical detector for squeezing, where by using broad phase matching techniques, the detection bandwidth can be almost unlimited (up to 100THz). We show that by measuring the quadrature amplitudes and noise of the sum-frequency light generated by an input of squeezed vacuum, the input squeezing level can be accurately deduced, especially with high-power input. In addition, the proposed scheme is robust to inefficiency / loss of the sum-frequency photons, which reduces the accuracy of the measurement, but does not impede it.