Acquisitions (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Significant Acquisitions and Disposals [Line Items]
Other Cost and Expense, Operating	$ 2,046	$ 5,036	$ 49,209	$ 11,512	$ 5,154	$ 6,718	$ 2,332	$ 1,889	$ 67,803	$ 16,093	$ 149,129
Payments to Acquire Businesses, Net of Cash Acquired									34,873	101,933	111,812
Acquisition And Other Related Costs [Member]
Significant Acquisitions and Disposals [Line Items]
Other Cost and Expense, Operating									$ 1,380	$ 25,549	$ 5,319