  We present the results of a comprehensive assessment of companions to
solar-type stars. A sample of 454 stars, including the Sun, was selected from
the Hipparcos catalog with {\pi} > 40 mas, {\sigma}_{\pi}/{\pi} < 0.05, 0.5 < B
- V < 1.0 (~ F6-K3), and constrained by absolute magnitude and color to exclude
evolved stars. New observational aspects of this work include surveys for (1)
very close companions with long-baseline interferometry at the CHARA Array, (2)
close companions with speckle interferometry, and (3) wide proper motion
companions identified by blinking multi-epoch archival images. In addition, we
include the results from extensive radial-velocity monitoring programs and
evaluate companion information from various catalogs.
  The overall observed fractions of single, double, triple, and higher order
systems are 56% \pm 2%, 33% \pm 2%, 8% \pm 1%, and 3% \pm 1%, respectively,
counting all confirmed stellar and brown dwarf companions. Our completeness
analysis indicates that only a few undiscovered companions remain in this
well-studied sample, implying that the majority (54% \pm 2%) of solar-type
stars are single, in contrast to the results of prior multiplicity studies. The
orbital-period distribution of companions is unimodal and roughly log-normal
with a peak of about 300 years. The period-eccentricity relation shows a
roughly flat distribution beyond the expected circularization for periods below
12 days. The mass-ratio distribution shows a preference for like-mass pairs,
which occur more frequently in relatively close pairs. The fraction of planet
hosts among single, binary, and multiple systems are statistically
indistinguishable, suggesting that planets are as likely to form around single
stars as they are around components of binary or multiple systems with
sufficiently wide separations.
