Fair Value Measurements (Measurment Inputs) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012	Jun. 30, 2011
Liabilities:
Contingent purchase price	$ 105,807	$ 18,971
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Assets:
Money market	42,170	14,751
U.S government agency notes	0	0
Corporate debt securities	0	0
Total assets at fair value	42,170	14,751
Liabilities:
Contingent purchase price	0	0
Total liabilities at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Assets:
Money market	0	0
U.S government agency notes	7,040	7,097
Corporate debt securities	16,652	43,778
Total assets at fair value	23,692	50,875
Liabilities:
Contingent purchase price	0	0
Total liabilities at fair value	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Assets:
Money market	0	0
U.S government agency notes	0	0
Corporate debt securities	0	0
Total assets at fair value	0	0
Liabilities:
Contingent purchase price	105,807	18,971	20,995	20,431
Total liabilities at fair value	105,807	18,971
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value, Fair Value Disclosure [Member]
Assets:
Money market	42,170	14,751
U.S government agency notes	7,040	7,097
Corporate debt securities	16,652	43,778
Total assets at fair value	65,862	65,626
Liabilities:
Contingent purchase price	105,807	18,971
Total liabilities at fair value	$ 105,807	$ 18,971