Quarterly report pursuant to sections 13 or 15(d)

Notes Receivable from Partners - Additional Information (Detail)

v2.4.0.8
Notes Receivable from Partners - Additional Information (Detail) (Partners, USD $)
In Thousands, unless otherwise specified
9 Months Ended
Sep. 30, 2013
Dec. 31, 2012
Dec. 31, 2011
Sep. 30, 2013
Limited Recourse
Dec. 31, 2012
Limited Recourse
Sep. 30, 2009
Limited Recourse
Aug. 31, 2009
Limited Recourse
Jan. 31, 2008
Limited Recourse
Sep. 30, 2013
Full Recourse
Dec. 31, 2012
Full Recourse
Related Party Transaction [Line Items]                    
Term of promissory notes receivable In the form of five or six year interest-bearing promissory notes and/or in the form of nine year interest-bearing limited recourse promissory notes                  
Interest rates of promissory notes           2.84% 2.77% 3.53%    
Notes receivable from partners $ 3,040 $ 3,410 $ 6,024 $ 1,953 $ 1,457       $ 1,661 $ 1,379