Operating Segment Information (Detail) - (Table 2) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2018	Mar. 31, 2017
Segment Reporting Information [Line Items]
Domestic	$ 389,014	$ 366,387
Geographical [Member]
Segment Reporting Information [Line Items]
Domestic	97,033	87,669
International [Member]
Segment Reporting Information [Line Items]
Domestic	47,446	34,992
Domestic [Member]
Segment Reporting Information [Line Items]
Domestic	$ 341,568	$ 331,395

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=63488584&loc=d3e20235-122688

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