Quarterly report pursuant to Section 13 or 15(d)

Accounting Policies and Recent Accounting Pronouncements - Additional Information (Detail)

v3.10.0.1
Accounting Policies and Recent Accounting Pronouncements - Additional Information (Detail)
9 Months Ended
Sep. 30, 2018
USD ($)
Segment
Dec. 31, 2017
USD ($)
Accounting Policies [Line Items]    
Number of reporting units | Segment 1  
Finite-lived intangible asset, amortization method Straight-line  
Marketable securities, available for sale $ 205,836,000 $ 125,659,000
Contingent consideration liability 1,806,000  
Accounting Standards Update 2018-02 [Member]    
Accounting Policies [Line Items]    
Reclassification of stranded tax effects from accumulated other comprehensive income to retained earnings 13,000  
Accounting Standards Update 2016-02 [Member]    
Accounting Policies [Line Items]    
Operating lease obligations 89,600,000  
Accounting Standards Update 2018-13 [Member]    
Accounting Policies [Line Items]    
Contingent consideration liability $ 1,806,000  
Minimum [Member]    
Accounting Policies [Line Items]    
Finite-lived intangible asset, useful life 1 year  
Maximum [Member]    
Accounting Policies [Line Items]    
Finite-lived intangible asset, useful life 6 years  
Average AA + Credit Rating [Member] | Accounting Standards Update 2016-13 [Member]    
Accounting Policies [Line Items]    
Marketable securities, available for sale $ 205,800,000  
Impairment write-downs marketable securities, available for sale $ 0  
Capitalization of Internal Labor [Member]    
Accounting Policies [Line Items]    
Property and equipment, useful life 5 years  
Costs related to development or purchases of internal -use software, depreciation method Straight-line