He is perhaps best known for his roles as Tom Frank in Robert Altman 's `` Nashville '' , Wild Bill Hickok in the HBO series `` Deadwood '' and FBI agent Frank Lundy in `` Dexter '' .
He is known for his roles as Tom Frank in Robert Altman 's `` Nashville '' , Wild Bill Hickok in the HBO series `` Deadwood '' and FBI agent Frank Lundy in `` Dexter '' .