Basis of Presentation (Narrative) (Detail)	9 Months Ended
	Sep. 30, 2012
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of offices	51
Delaware [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of offices	42
Pennsylvania [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of offices	7
Virginia [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of offices	1
Nevada [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of offices	1