Fair Value Measurements (Assets and Liabilities Measured at Fair Value on a Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Short-term investments and available-for-sale securities	$ 6,018	[1]	$ 22,270	[1]
Interest rate swap agreements	5,442	[1],[2]
Aquisition-related contingent consideration	23,711		25,617		5,809
Fair Value, Inputs, Level 1 [Member]
Short-term investments and available-for-sale securities	6,018	[1]	22,270	[1]
Fair Value, Inputs, Level 2 [Member]
Interest rate swap agreements	5,442	[1],[2]
Fair Value, Inputs, Level 3 [Member]
Aquisition-related contingent consideration	$ 23,711		$ 25,617

[1] Consists of interest rate swap agreements based on JIBAR and IBR 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.

[2] Consists of highly liquid investments with original maturities in excess of three months.