Fair Value Measurements (Assets and Liabilities Measured at Fair Value on Recurring Basis) (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Liabilities:
Contingent purchase price	$ 79,227	$ 82,289
Fair Value, Measurements, Recurring
Assets:
Money market	56,198	56,097
Total assets at fair value	56,198	56,097
Liabilities:
Contingent purchase price	124,735	137,289
Total liabilities at fair value	124,735	137,289
Fair Value, Measurements, Recurring | Quoted Prices In Active Markets for Identical Assets (Level 1)
Assets:
Money market	56,198	56,097
Total assets at fair value	56,198	56,097
Liabilities:
Contingent purchase price	0	0
Total liabilities at fair value	0	0
Fair Value, Measurements, Recurring | Significant Other Observable Inputs (Level 2)
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 | Significant Unobservable Inputs (Level 3)
Assets:
Money market	0	0
Total assets at fair value	0	0
Liabilities:
Contingent purchase price	124,735	137,289
Total liabilities at fair value	$ 124,735	$ 137,289