Annual report pursuant to Section 13 and 15(d)

Stock-based Compensation - Summary of Stock Option Transactions Under Equity Plan, Stock Incentive Plan, Multifamily Technology Solutions Plan and Board Plan (Detail)

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Stock-based Compensation - Summary of Stock Option Transactions Under Equity Plan, Stock Incentive Plan, Multifamily Technology Solutions Plan and Board Plan (Detail) - $ / shares
12 Months Ended
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Number of Shares      
Number of Shares, Beginning Balance 5,566,888 5,914,802 5,858,613
Number of Shares, Granted 2,434,198 1,934,031 2,421,124
Number of Shares, Exercised (809,303) (907,765) (1,556,865)
Number of Shares, Forfeited/cancelled (1,389,910) (1,336,894) (800,470)
Number of Shares, Expired   (37,286) (7,600)
Number of Shares, ending balance 5,801,873 5,566,888 5,914,802
Range of Exercise Prices      
Range of exercise prices beginning balance, lower limit (in dollars per share) $ 0.91 $ 0.91 $ 0.91
Range of exercise prices beginning balance, upper limit (in dollars per share) 29.5 29.50 29.50
Range of exercise prices, Granted lower limit (in dollars per share) 18.79 15.19 19.78
Range of exercise prices, Granted upper limit (in dollars per share) 23.1 21.54 25.70
Range of exercise prices Exercised, lower limit (in dollars per share) 0.91 0.91 0.91
Range of exercise prices Exercised, upper limit (in dollars per share) 21.6 21.6 25.24
Range of exercise prices Forfeited/cancelled, lower limit (in dollars per share) 5.04 4.28 4.28
Range of exercise prices Forfeited/cancelled, upper limit (in dollars per share) 29.5 29.5 29.50
Range of exercise prices Expired, lower limit (in dollars per share)   19.78 24.03
Range of exercise prices Expired, upper limit (in dollars per share)   24.64 24.64
Range of exercise prices Ending Balance, lower limit (in dollars per share) 0.91 0.91 0.91
Range of exercise prices Ending Balance, upper limit (in dollars per share) 29.5 29.5 29.50
Weighted-Average Exercise Price      
Weighted average exercise price, Beginning Balance (in dollars per share) 18.89 18.56 13.97
Weighted average exercise price, Granted (in dollars per share) 19.81 17.68 22.20
Weighted average exercise price, Exercised (in dollars per share) 14.97 10.92 6.81
Weighted average exercise price, Forfeited/cancelled (in dollars per share) 20.54 20.93 18.71
Weighted average exercise price, Expired (in dollars per share)   24.02 24.35
Weighted average exercise price, Ending Balance (in dollars per share) $ 19.43 $ 18.89 $ 18.56