Operating Segment Information - Summary of Company's Revenue by Geographical Region (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Revenues [Abstract]
Revenue	$ 174,653	$ 165,676
United States
Revenues [Abstract]
Revenue	143,428	119,053
United Kingdom
Revenues [Abstract]
Revenue	25,909	44,336
Other International Countries
Revenues [Abstract]
Revenue	$ 5,316	$ 2,287

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 225
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration