Development of a fully-implicit, Giles-type nonreflecting boundary condition in a computational fluid dynamics solver using a discontinuous Galerkin method on Chimera overset grids is demonstrated. The implicit formulation is in the context of Newton's method. The implementation was completed without the use of ghost elements or extra degrees of freedom in the system of equations and the boundary condition is not lagged. Rather, the elements associated with the nonreflecting boundary are fully-coupled with each other in the Newton linearization. The linearization of the governing equations and boundary conditions is achieved via an automatic differentiation technique based on operator overloading. Calculations of a turbine cascade geometry using truncated and extended domains were computed. Comparison of pressure and flow angles at the exit plane location between the truncated and extended domains were very well matched. All calculations converged in 4-7 Newton iterations up through 4 th -order accuracy.