The Business, Basis of Presentation and Summary of Significant Accounting Policies - Recent Accounting Pronouncements (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Excess tax benefit amount		$ (7,700,000)
Stock-based compensation expenses		7,642,000	$ 12,872,000	$ 15,368,000
Restricted cash		0
Accounting Standard Update 2016-18
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Restricted cash		$ 1,300,000
Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Stock-based compensation expenses	$ 600,000
Additional paid-in capital | Accounting Standards Update 2016-09
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect of new accounting principle	$ 600,000