New Accounting Pronouncements - Select Unaudited Consolidated Statement of Operations Line Items (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Impact of Recently Adopted Accounting Standards
Revenue	$ 50,992	$ 38,691	$ 99,426	$ 74,636
Gross profit	39,888	30,300	78,107	58,644
Sales and marketing	35,161	24,731	65,839	49,090
Total operating expenses	59,095	42,717	115,121	83,552
Loss from operations	(19,207)	(12,417)	(37,014)	(24,908)
Loss before income taxes	(25,247)	(12,266)	(45,770)	(24,688)
Net loss	(25,281)	(12,335)	(45,875)	(24,774)
Comprehensive loss	(25,281)	(12,335)	(45,875)	(24,774)
Net loss attributable to common stockholders	$ (184,734)	$ (9,012)	$ (245,367)	$ (33,098)
Net loss per share attributable to common stockholders - basic and diluted	$ (4.13)	$ (0.88)	$ (8.73)	$ (3.27)
Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Impact of Recently Adopted Accounting Standards
Revenue		$ 39,059		$ 75,821
Gross profit		30,668		59,829
Sales and marketing		25,727		51,024
Total operating expenses		43,713		85,486
Loss from operations		(13,045)		(25,657)
Loss before income taxes		(12,894)		(25,437)
Net loss		(12,963)		(25,523)
Comprehensive loss		(12,963)		(25,523)
Net loss attributable to common stockholders		$ (9,640)		$ (33,847)
Net loss per share attributable to common stockholders - basic and diluted		$ (0.94)		$ (3.35)
Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Impact of Recently Adopted Accounting Standards
Revenue		$ (368)		$ (1,185)
Gross profit		(368)		(1,185)
Sales and marketing		(996)		(1,934)
Total operating expenses		(996)		(1,934)
Loss from operations		628		749
Loss before income taxes		628		749
Net loss		628		749
Comprehensive loss		628		749
Net loss attributable to common stockholders		$ 628		$ 749
Net loss per share attributable to common stockholders - basic and diluted		$ 0.06		$ 0.07
Subscription, License and Support
Impact of Recently Adopted Accounting Standards
Revenue	$ 47,891	$ 35,749	$ 93,282	$ 68,754
Subscription, License and Support | Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Impact of Recently Adopted Accounting Standards
Revenue		35,828		69,567
Subscription, License and Support | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Impact of Recently Adopted Accounting Standards
Revenue		(79)		(813)
Services
Impact of Recently Adopted Accounting Standards
Revenue	$ 3,101	2,942	$ 6,144	5,882
Services | Accounting Standards Update 2014-09 | Calculated under Revenue Guidance in Effect before Topic 606
Impact of Recently Adopted Accounting Standards
Revenue		3,231		6,254
Services | Accounting Standards Update 2014-09 | Difference between Revenue Guidance in Effect before and after Topic 606
Impact of Recently Adopted Accounting Standards
Revenue		$ (289)		$ (372)