Fair Value Measurement (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012		Jun. 30, 2012	Dec. 31, 2011		Sep. 30, 2011	Jun. 30, 2011	Dec. 31, 2010
Aquisition-related contingent consideration	$ 27,209		$ 29,897	$ 25,617		$ 8,182	$ 5,671	$ 5,809
Fair Value, Measurements, Recurring [Member]
Short-term investments and available-for-sale securities				22,270	[1]
Interest rate swap agreements	2,454	[2]
Aquisition-related contingent consideration	27,209			25,617
Fair Value, Inputs, Level 1 [Member] | Fair Value, Measurements, Recurring [Member]
Short-term investments and available-for-sale securities				22,270	[1]
Fair Value, Inputs, Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Interest rate swap agreements	2,454	[2]
Fair Value, Inputs, Level 3 [Member] | Fair Value, Measurements, Recurring [Member]
Aquisition-related contingent consideration	$ 27,209			$ 25,617

[1] Consists of certain short-term investments that are highly liquid and actively traded in over-the-counter markets as well as available-for-sale securities traded in active markets.

[2] Consists of interest rate swap agreements based on JIBAR whose value is determined using a pricing model with inputs that are observable in the market or can be derived principally from, or corroborated by, observable market data.