Employee Incentive and Retirement Plans - Additional Information (Detail)		3 Months Ended			12 Months Ended
	Jun. 22, 2016 position	Mar. 31, 2017	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) EquityPlan $ / shares shares	Dec. 31, 2016 USD ($) $ / shares shares	Dec. 31, 2015 USD ($) $ / shares shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Tax deficits (benefits)						$ 200,000	$ (700,000)
Number of options to purchase common stock granted under the 2007 Plan (shares) | shares					20,409,340	30,669,177
Grants (shares) | shares					0	7,482,011
Grants ($ per share) | $ / shares					$ 0.00	$ 7.22
Total intrinsic value of options exercised					$ 27,000,000	$ 74,400,000	103,500,000
Total fair value of stock options vested					$ 19,600,000	$ 32,900,000	$ 36,800,000
Total shares available for future issuance (shares) | shares					105,511,561	95,940,598
Service period					90 days
Employer 401(k) plan match to employee's eligible earnings, percentage				4.00%			3.00%
Employer maximum annual match per employee for 401(k) plan				$ 5,000			$ 5,000
Expected headcount reduction	12.00%
Severance expense					$ 0	$ 2,730,000	0
Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of positions expected to be eliminated | position	179
Pension Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Employer 401 (k) total match expense					4,400,000	$ 3,900,000	$ 2,100,000
Stock issued related to acquisition | Series F Convertible Preferred Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Business acquisition, shares consideration					25,000,000
Business acquisition, value of shares placed in third party escrow to secure retention of key employees					$ 22,100,000
Vesting period for compensation arrangement					3 years
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Requisite service period		1 year
Performance Shares [Member] | Maximum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Issuance Range		200.00%
Performance Shares [Member] | Minimum
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Award Issuance Range		0.00%
Equity Option
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants (shares) | shares							1,164,929
Grants ($ per share) | $ / shares							$ 20.00
Common stock, Weighted average grant date fair value per share ($ per share) | $ / shares						$ 3.61	$ 9.80
Fair value						$ 27,000,000	$ 11,400,000
Unrecognized compensation cost					$ 13,900,000
Unrecognized compensation cost expected period for recognition					1 year 9 months 18 days
Employee Stock Option - Vested
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Grants (shares) | shares						265,987
RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost expected period for recognition					2 years 10 months 24 days
Grants ($ per share) | shares					12,955,901.000000
Fair value					$ 68,800,000
Unrecognized compensation cost					$ 150,400,000
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Unrecognized compensation cost expected period for recognition					6 months
Offering period					6 months
Purchase price					85.00%
Issuance of common stock in connection with employee stock purchase plan (in shares) | shares					1,319,537	1,508,513	410,009
Total shares available for future issuance (shares) | shares					8,695,999	5,408,441	2,589,991
Requisite service period					6 months
Developing software
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Stock-based compensation expense, capitalized amount					$ 9,200,000	$ 9,800,000	$ 4,400,000
Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of equity incentive plans | EquityPlan					2
Equity Incentive Plan Two Thousand Seven
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of options to purchase common stock granted under the 2007 Plan (shares) | shares					15,500,667
Equity Incentive Plan Twenty Fourteen
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total number of shares available for future grants (shares) | shares					49,277,465
Executive Management And Key Personnel
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash awarded			$ 18,600,000
Executive Management And Key Personnel | RSUs
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Equity awarded			$ 16,300,000