Equity-Based Compensation - Activity of RDUs Available for Future Grants (Detail)	6 Months Ended
	Jun. 30, 2013
Activity of RDUs available for future grants
Restricted Depository Units Available For Future Grants, Beginning Balance	1,685,345
Restricted Depository Units Available For Future Grants, Purchases	6,236
Restricted Depository Units Available For Future Grants, Granted
Restricted Depository Units Available For Future Grants, Forfeited
Restricted Depository Units Available For Future Grants, Ending Balance	1,691,581