Goodwill and Intangible Assets - Additional Information (Details) - USD ($)	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Goodwill and Intangible Assets Disclosure [Abstract]
Amortization expense									$ 7,400,000	$ 9,300,000	$ 10,600,000
Amortization of certain acquired intangible assets	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 150,000	0	150,000	600,000
Impairment charges									0	0	$ 0
Change in carrying amount of goodwill									$ 0	$ 0