Stock Based Compensation - Additional Information (Detail) - USD ($)	1 Months Ended						12 Months Ended
	Jul. 31, 2018	Dec. 31, 2017	Jun. 30, 2017	Mar. 31, 2017	Sep. 30, 2016	Oct. 31, 2015	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2016	Jun. 30, 2016	Sep. 30, 2014	Jun. 30, 2013	Jun. 30, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Term of award							10 years
Share based compensation granted under plan vest period							4 years
Weighted-average grant date fair value per share of stock-based awards, granted to employees							$ 70.93	$ 44.66	$ 14.78
Stock-based compensation expense							$ 78,602,000	$ 50,127,000	$ 30,465,000
Unrecognized stock based compensation expense							$ 181,100,000
Weighted average period expected to recognize unrecognized stock base compensation expense							3 years
Options with Service conditions [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock based compensation expense							$ 109,500,000
Awards with Service and Market Conditions [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock based compensation expense							22,100,000
Stock Awards or Stock Units with Service Conditions [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock based compensation expense							49,500,000
Former Chief Executive Officer [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense									2,100,000
Maximum [Member] | Awards with Performance Conditions [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized stock based compensation expense							100,000
Stock Options with Performance-based Conditions [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense							$ 100,000	$ 200,000	$ 900,000
Restricted Stock Awards (RSAs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants, Restricted stock units and awards								27,590	341,500
Grant date fair value, restricted stock units and awards								$ 98.57	$ 34.58
Restricted stock units and awards with performance conditions remaining to be vested		411,781					136,125	252,321	411,781			153,170
Restricted Stock Awards (RSAs) [Member] | Minimum [Member] | Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense									$ 0
Grants, Restricted stock units and awards					71,925
Share-based compensation award, expiration date		Jun. 30, 2018
Grant date fair value, restricted stock units and awards					$ 48.94
Restricted Stock Awards (RSAs) [Member] | Maximum [Member] | Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense								$ 3,300,000
Grants, Restricted stock units and awards					89,906
Share-based compensation award, expiration date		Jan. 01, 2019
Grant date fair value, restricted stock units and awards					$ 54.29
Restricted Stock Units (RSUs) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants, Restricted stock units and awards							511,283	230,736	181,029
Grant date fair value, restricted stock units and awards							$ 131.18	$ 87.95	$ 33.03
Restricted stock units and awards with performance conditions remaining to be vested		66,552					605,874	251,298	66,552
Restricted Stock Units (RSUs) [Member] | Executives [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense							$ 500,000	$ 200,000	$ 2,900,000
Grants, Restricted stock units and awards				156,029
Restricted stock units and awards with performance conditions remaining to be vested							0
2011 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock remain available for future grant							0
Number of shares approved under the plan																16,000,000.0
2013 Employee Stock Purchase Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock remain available for future grant							600,000
Number of shares approved under the plan										500,000			300,000		300,000
Term of award							24 months
Percentage of closing price of common stock							85.00%
2013 Employee Stock Purchase Plan [Member] | Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation award, expiration date							Feb. 29, 2020
2013 Employee Stock Purchase Plan [Member] | Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation award, expiration date							Aug. 31, 2021
2014 Employment Commencement Incentive Plan (2014 Plan) [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock remain available for future grant							600,000
Number of shares approved under the plan														600,000
Number of additional shares approved under the plan	1,200,000		3,800,000			1,000,000.0
2018 Equity Incentive Plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Common stock remain available for future grant							3,400,000
Number of shares approved under the plan											2,900,000