Commitments and Contingencies - Approximate Aggregate Minimum Future Rental Payments Required (Parenthetical) (Details) (GCP Capital Partners Holdings LLC [Member], USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Apr. 30, 2011 sqft
GCP Capital Partners Holdings LLC [Member]
Commitments and Contingencies Disclosure [Line Items]
Future Minimum Payments Due on Sublease	$ 1.1
Number Of Leasable Square Feet		15,000