Segment Information - Company's Reportable Segments (Details)	9 Months Ended
	Sep. 30, 2012
Northeast Region [Member]
Segment Reporting Information [Line Items]
Markets in Consolidated Regions	Southeastern PA; Lehigh/Central PA; New Jersey; Maryland
Central Region [Member]
Segment Reporting Information [Line Items]
Markets in Consolidated Regions	Minnesota; Chicago/Milwaukee; Houston; Arizona
South Region [Member]
Segment Reporting Information [Line Items]
Markets in Consolidated Regions	Richmond/Hampton Roads; Carolinas; Jacksonville; Orlando; South Florida; Tampa
Metro [Member]
Segment Reporting Information [Line Items]
Markets in Consolidated Regions	Philadelphia; Metro Washington, D.C.
United Kingdom [Member]
Segment Reporting Information [Line Items]
Markets in Consolidated Regions	County of Kent; West Midlands