Stockholders' Equity and Employee Benefit Plans - 401(k) Plan - Additional Information (Details) - United States - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Mar. 31, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Defined Contribution Plan Disclosure [Line Items]
Matching contribution of deferrals for eligible employees			25.00%
Matching contribution compensation expense	$ 0.5	$ 0.4	$ 1.8	$ 1.5

Amount of cost for defined contribution plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 70
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=49170846&loc=d3e28014-114942

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration