Fair Value Measurements (Narrative) (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013	Dec. 31, 2013	Dec. 31, 2012
Fair Value Measurements [Abstract]
Accrued earnouts	$ 19,779,000	$ 7,015,000	$ 19,779,000	$ 7,015,000	$ 30,063,000	$ 9,840,000
Performance targets, maximum potential obligation	31,600,000		31,600,000
Impairment charge recognized, related to long-lived assets	4,000,000	6,500,000	7,600,000	10,200,000
Write-offs relating to long-lived assets and intangibles	3,300,000	6,100,000	5,600,000	7,400,000
Certificate of deposits	5,600,000		5,600,000		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
Interest rate under Revolving Credit Facility			1.875%