  We present extensive photometry at ultraviolet (UV), optical, and
near-infrared (NIR) wavelengths, as well as dense sampling of optical spectra,
for the normal type Ia supernova (SN Ia) 2005cf. From the well-sampled light
curves, we find that SN 2005cf reached a B-band maximum at 13.63+/-0.02 mag,
with an observed luminosity decline rate dm_15(B) = 1.05+/-0.03 mag. The
correlations between the decline rate and various color indexes, recalibrated
on the basis of an expanded SN Ia sample, yielded E(B-V)_host=0.09+/-0.03 mag
for SN2005cf. The UV photometry was obtained with the HST and the Swift
Ultraviolet/Optical Telescope, and the results match each other to within
0.1-0.2 mag. The UV light curves show similar evolution to the broadband U,
with an exception in the 2000-2500 Angstrom spectral range (corresponding to
the F220W/uvm2 filters), where the light curve appears broader and much fainter
than that on either side (likely owing to the intrinsic spectral evolution).
Combining the UV data with the ground-based optical and NIR data, we establish
the generic UV-optical-NIR bolometric light curve for SN 2005cf and derive the
bolometric corrections in the absence of UV and/or NIR data. The overall
spectral evolution of SN 2005cf is similar to that of a normal SN Ia, but with
variety in the strength and profile of the main feature lines. The spectra at
early times displayed strong, detached high-velocity (HV) features in the Ca II
H&K doublet and NIR triplet. Similar HV features may exist in the SiII 6355
absorption line which evolved rapidly from a flat-bottomed feature in the
earliest phase to a triangular shape one week before maximum, and may be common
in other normal SNe Ia. The possible origin of the HV absorption features is
briefly discussed (abridged).
