Employee Incentive and Retirement Plans - Options Activity Under Option Plan (Detail) (USD $) In Thousands, except Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 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	768,500
Options Exercised, Number of Shares	(531,822)	(1,439,124)
Options Forfeited/Expired, Number of Shares	(390,152)
Balances, ending balance, Number of Shares	57,233,355
Vested and expected to vest, Number of Shares	56,450,213
Exercisable, Number of Shares	24,343,206
Balances, beginning balance, Weighted Average Exercise Price Per Share	$ 3.15
Options Granted, Weighted Average Exercise Price Per Share	$ 20.81
Options Exercised, Weighted Average Exercise Price Per Share	$ 1.62
Options Forfeited/Expired, Weighted Average Exercise Price Per Share	$ 7.11
Balances, ending balance, Weighted Average Exercise Price Per Share	$ 3.37
Vested and expected to vest, Weighted Average Exercise Price Per Share	$ 3.29
Exercisable, Weighted Average Exercise Per Share	$ 0.92
Outstanding, Weighted Average Remaining Contractual Life	7 years 9 months 22 days
Vested and expected to vest, Weighted Average Remaining Contractual Life	7 years 9 months 6 days
Exercisable, Weighted Average Remaining Contractual Life	6 years 7 months 25 days
Outstanding, Aggregate Intrinsic Value	$ 932,931
Vested and expected to vest, Aggregate Intrinsic Value	924,352
Exercisable, Aggregate Intrinsic Value	$ 461,441