Fair Value Measurements (Narrative) (Details) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Accrued earnouts	$ 23,136,000	$ 25,965,000	$ 23,136,000	$ 25,965,000	$ 30,063,000	$ 9,840,000
Performance targets, maximum potential obligation	35,700,000		35,700,000
Impairment charge recognized, related to long-lived assets	6,000,000	6,200,000	13,600,000	16,400,000
Write-offs relating to long-lived assets and intangibles	5,200,000	4,900,000	10,800,000	12,300,000
Certificate of deposits	5,300,000		5,300,000		5,200,000
Held-to-maturity investments, carrying value	1,200,000		1,200,000		1,100,000
Held-to-maturity investments, fair value	$ 1,300,000		$ 1,300,000		$ 1,300,000
Minimum [Member]
Basis spread on variable interest rate			1.875%
Maximum [Member]
Basis spread on variable interest rate			2.375%