Summary of Significant Accounting Policies - Additional Information (Details) shares in Thousands	12 Months Ended
	Dec. 31, 2017 USD ($) Customer shares	Dec. 31, 2016 USD ($) Customer shares	Dec. 31, 2015 USD ($) shares
Summary Of Significant Accounting Policies [Line Items]
Sales rebates	$ 200,000		$ 100,000
Number of customers accounted for more than 10% of accounts receivable | Customer	0	0
Disbursement of pre-funded study costs	$ 138,700,000	$ 150,300,000	114,400,000
Fair value measurements transfers between level 1, level 2, or level 3	$ 0	$ 0	$ 0
Stock Options
Summary Of Significant Accounting Policies [Line Items]
Antidilutive securities excluded from computation of diluted EPS | shares	63	0	1,794
RSAs and RSUs
Summary Of Significant Accounting Policies [Line Items]
Antidilutive securities excluded from computation of diluted EPS | shares	0	0	660
Maximum
Summary Of Significant Accounting Policies [Line Items]
Sales rebates		$ 100,000
Estimated useful life of intangible assets	15 years
Maximum | Accounting Standard Update (“ASU”) No. 2016-09
Summary Of Significant Accounting Policies [Line Items]
Discrete Adjustments to Income Tax Expense Benefit	$ 100,000
Maximum | Computer Hardware Software Phone and Medical Imaging Equipment
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of assets	5 years
Maximum | Furniture and Fixtures and Other Equipment
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of assets	7 years
Maximum | Buildings
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of assets	40 years
Maximum | Computer Software Developed Costs
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of assets	3 years
Minimum
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of intangible assets	17 months
Minimum | Computer Hardware Software Phone and Medical Imaging Equipment
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of assets	3 years
Minimum | Furniture and Fixtures and Other Equipment
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of assets	5 years
Minimum | Buildings
Summary Of Significant Accounting Policies [Line Items]
Estimated useful life of assets	30 years
Miscellaneous Expense, Net
Summary Of Significant Accounting Policies [Line Items]
Net loss on foreign currency transactions	$ (1,000,000)	(700,000)	$ (1,300,000)
Selling, General and Administrative
Summary Of Significant Accounting Policies [Line Items]
Advertisement expenses	$ 600,000	$ 600,000	$ 400,000