Segment Information - Total Assets by Segment (Details) (USD $)	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 4,989,673,000	$ 5,064,799,000
Corporate [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	37,209,000	137,290,000
Segment, Geographical, Domestic [Member] | Northeast Southeastern PA [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	842,779,000	857,762,000
Segment, Geographical, Domestic [Member] | Northeast Lehigh/Central PA [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	716,772,000	749,137,000
Segment, Geographical, Domestic [Member] | Northeast Other [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	424,005,000	438,613,000
Segment, Geographical, Domestic [Member] | Central Region [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	991,776,000	967,170,000
Segment, Geographical, Domestic [Member] | South Region [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	1,448,849,000	1,506,972,000
Segment, Geographical, Domestic [Member] | Metro [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	383,725,000	281,258,000
Statement, Geographical, Foreign [Member] | United Kingdom [Member]
Segment Reporting, Asset Reconciling Item [Line Items]
Assets	$ 144,558,000	$ 126,597,000