Employee Incentive and Retirement Plans - Options Activity Under Option Plan (Detail) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014
Share Based Compensation Arrangement By Share Based Payment Award Options Outstanding Roll Forward
Balances, beginning balance, Number of Shares	57,386,829
Options Granted, Number of Shares	1,164,929
Options Exercised, Number of Shares	(5,407,540)	(5,638,830)
Options Forfeited/Expired, Number of Shares	(1,844,875)
Balances, ending balance, Number of Shares	51,299,343
Vested and expected to vest, Number of Shares	50,807,451
Exercisable, Number of Shares	26,216,233
Balances, beginning balance, Weighted Average Exercise Price Per Share	$ 3.15
Options Granted, Weighted Average Exercise Price Per Share	20.00
Options Exercised, Weighted Average Exercise Price Per Share	1.46
Options Forfeited/Expired, Weighted Average Exercise Price Per Share	6.45
Balances, ending balance, Weighted Average Exercise Price Per Share	3.59
Vested and expected to vest, Weighted Average Exercise Price Per Share	3.54
Exercisable, Weighted Average Exercise Per Share	$ 1.58
Outstanding, Weighted Average Remaining Contractual Life	7 years 3 months 18 days
Vested and expected to vest, Weighted Average Remaining Contractual Life	7 years 3 months 18 days
Exercisable, Weighted Average Remaining Contractual Life	6 years 6 months
Outstanding, Aggregate Intrinsic Value	$ 503,203
Vested and expected to vest, Aggregate Intrinsic Value	500,401
Exercisable, Aggregate Intrinsic Value	$ 306,781