XML 81 R35.htm IDEA: XBRL DOCUMENT v3.8.0.1
Summary of Significant Accounting Policies - Summary of Reflection of New Adopted Standards in Selected Consolidated Statement of Operations Line Items (Detail) - USD ($)
$ / shares in Units, $ in Thousands
 3 Months Ended 12 Months Ended
Dec. 31, 2017
Sep. 30, 2017
Jun. 30, 2017
Mar. 31, 2017
Dec. 31, 2016
Sep. 30, 2016
Jun. 30, 2016
Mar. 31, 2016
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Costs and expenses:                      
Sales and marketing                 $ 150,512 $ 119,258 $ 92,554
General and administrative                 91,647 69,046 47,826
Operating income $ 19,434 $ 11,437 $ 9,089 $ 38,665 $ 12,681 $ 582 $ 16,004 $ 28,704 78,625 57,971 34,435
Net income                 $ 66,807 $ 43,840 $ 20,945
Earnings per share, basic $ 0.22 $ 0.24 $ 0.24 $ 0.44 $ 0.15 $ 0.11 $ 0.18 $ 0.32 $ 1.15 $ 0.76 $ 0.37
Earnings per share, diluted $ 0.22 $ 0.24 $ 0.24 $ 0.43 $ 0.15 $ 0.10 $ 0.18 $ 0.31 $ 1.13 $ 0.74 $ 0.36
Accounting Standards Update 2014-09 [Member]                      
Costs and expenses:                      
Sales and marketing                 $ 110,846 $ 85,361  
General and administrative                 80,228 59,174  
Operating income                 129,710 101,740  
Net income                 $ 123,486 $ 70,421  
Earnings per share, basic                 $ 2.13 $ 1.21  
Earnings per share, diluted                 $ 2.10 $ 1.19