Fair Value Measurements (Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Dec. 31, 2013
Liabilities:
Contingent purchase price	$ 135,907		$ 140,712
Fair Value, Measurements, Recurring [Member]
Assets:
Money market	6,032		6,030
Total assets at fair value	6,032		6,030
Liabilities:
Contingent purchase price	204,307		351,134
Total liabilities at fair value	204,307		351,134
Fair Value, Measurements, Recurring [Member] | Quoted Prices In Active Markets for Identical Assets (Level 1) [Member]
Assets:
Money market	6,032		6,030
Total assets at fair value	6,032		6,030
Liabilities:
Contingent purchase price	0		0
Total liabilities at fair value	0		0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Assets:
Money market	0		0
Total assets at fair value	0		0
Liabilities:
Contingent purchase price	0		0
Total liabilities at fair value	0		0
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Assets:
Money market	0		0
Total assets at fair value	0		0
Liabilities:
Contingent purchase price	204,307	$ 207,160	351,134	$ 368,994	$ 360,780	$ 302,363
Total liabilities at fair value	$ 204,307		$ 351,134