Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013 Security	Dec. 31, 2014	Jan. 18, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability	$ 15,700	$ 17,200	$ 15,900
Auction rate securities	2,208	0
Amount of temporary impairment	192
Summarize the amortized cost basis, the aggregate fair value and gross unrealized holding [Abstract]
Amortized Cost Basis	2,400
Fair Value	2,208
Gross Unrealized Holding, Gains	0
Gross Unrealized Holding, Losses	(192)
Gross Unrealized Holding Gains (Losses), Net	(192)
Continuous unrealized loss position, Unrealized Losses [Abstract]
Number of securities with gross unrealized loss position	1
Weighted average duration of unrealized losses	70 months
Contingent consideration liability	15,700	17,200	15,900
Maximum [Member]
Continuous unrealized loss position, Unrealized Losses [Abstract]
Severity of the unrealized losses below amortized cost (in hundredths)	8.00%
Maturities Greater Than Ten Years [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Amount of temporary impairment	192
Summarize the amortized cost basis, the aggregate fair value and gross unrealized holding [Abstract]
Amortized Cost Basis	2,400
Fair Value	2,208
Gross Unrealized Holding, Gains	0
Gross Unrealized Holding, Losses	(192)
Gross Unrealized Holding Gains (Losses), Net	(192)
U.S. Government Subsidized Securities [Member] | Minimum [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Maturity period of US government subsidized securities (in years)	10 years
U.S. Government Subsidized Securities [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Auction rate securities	2,208
Auction Rate Securities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Auction rate securities	2,208
Continuous unrealized loss position, Fair Value [Abstract]
Less than 12 Months, Fair Value	0
12 Months or Greater, Fair Value	2,208
Total, Fair Value	2,208
Continuous unrealized loss position, Unrealized Losses [Abstract]
Less than 12 Months, Unrealized Losses	0
12 Months or Greater, Unrealized Losses	(192)
Total, Unrealized Losses	(192)
Recurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability	15,700	17,200
Money market funds	60,364	112,808
Auction rate securities	2,208
Liability, total	15,700	17,200
Asset, total	62,572	112,808
Continuous unrealized loss position, Unrealized Losses [Abstract]
Contingent consideration liability	15,700	17,200
Recurring [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability	0	0
Money market funds	60,364	112,808
Auction rate securities	0
Liability, total	0	0
Asset, total	60,364	112,808
Continuous unrealized loss position, Unrealized Losses [Abstract]
Contingent consideration liability	0	0
Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability	0	0
Money market funds	0	0
Auction rate securities	0
Liability, total	0	0
Asset, total	0	0
Continuous unrealized loss position, Unrealized Losses [Abstract]
Contingent consideration liability	0	0
Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Contingent consideration liability	15,700	17,200
Money market funds	0	0
Auction rate securities	2,208
Liability, total	15,700	17,200
Asset, total	2,208	0
Continuous unrealized loss position, Unrealized Losses [Abstract]
Contingent consideration liability	$ 15,700	$ 17,200