Segment Information - Costs Incurred on Long-lived Assets (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Segment Reporting Information [Line Items]
Costs incurred on long - lived assets	$ 512,017	$ 437,073	$ 134,147
Northeast Southeastern PA [Member]
Segment Reporting Information [Line Items]
Costs incurred on long - lived assets	11,577	14,851	9,567
Northeast Lehigh and Central PA [Member]
Segment Reporting Information [Line Items]
Costs incurred on long - lived assets	86,245	66,472	26,139
Northeast Other [Member]
Segment Reporting Information [Line Items]
Costs incurred on long - lived assets	10,943	9,232	11,974
Central Region [Member]
Segment Reporting Information [Line Items]
Costs incurred on long - lived assets	173,142	119,654	28,042
South Region [Member]
Segment Reporting Information [Line Items]
Costs incurred on long - lived assets	129,705	123,833	53,192
Metro [Member]
Segment Reporting Information [Line Items]
Costs incurred on long - lived assets	94,295	98,193	428
United Kingdom [Member]
Segment Reporting Information [Line Items]
Costs incurred on long - lived assets	$ 6,110	$ 4,838	$ 4,805