Commitments and Contingencies (Details) (USD $)	Dec. 31, 2012
Commitments and Contingencies
Monthly amount paid to an executive officer in consideration of noncompete covenants (as a percent)	50.00%
Minimum
Commitments and Contingencies
Estimated contingent liability related to employment, severance and noncompete agreements	9,000,000
Estimated tax gross ups payable under the agreement, due to change in control	1,100,000
Maximum
Commitments and Contingencies
Estimated contingent liability related to employment, severance and noncompete agreements	10,900,000
Estimated tax gross ups payable under the agreement, due to change in control	3,000,000