Revenue - Summary of Asset Balances and Related Amortization Expense For Contract Costs (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2019	Mar. 31, 2018
Costs to Obtain a Contract [Member]
Capitalized Contract Cost [Line Items]
Beginning Balance	$ 158,989	$ 126,207
Capitalization of Costs	19,387	15,122
Amortization	(5,721)	(4,418)
Ending Balance	172,655	136,911
Costs to Fulfill a Contract [Member]
Capitalized Contract Cost [Line Items]
Beginning Balance	101,756	72,061
Capitalization of Costs	15,005	11,043
Amortization	(3,470)	(2,515)
Ending Balance	$ 113,291	$ 80,589

Amount, after allowance for credit loss, of right to consideration in exchange for good or service transferred to customer when right is conditioned on something other than passage of time.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130531-203044

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 50
-Paragraph 8
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109196051&loc=SL49130549-203045

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 606
-SubTopic 10
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=82913815&loc=SL49130533-203044

Name:	us-gaap_ContractWithCustomerAssetNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant