Annual report pursuant to Section 13 and 15(d)

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

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Summary of Stock Option Transactions Under Equity Plan, Stock Incentive Plan, Multifamily Technology Solutions Plan and Board Plan (Detail) (USD $)
12 Months Ended
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Number of Shares      
Outstanding, Beginning Balance 7,292,031 9,131,494 7,928,729
Granted 1,641,470 1,477,250 2,460,600
Assumed MTS Plan   349,693  
Exercised (2,389,704) (3,117,058) (778,746)
Forfeited/cancelled (684,154) (547,969) (479,089)
Expired (1,030) (1,379)  
Number of Shares, ending balance 5,858,613 7,292,031 9,131,494
Range of exercise prices beginning balance, lower limit $ 0.91 $ 2.00 $ 2
Range of exercise prices beginning balance, upper limit $ 29.50 $ 27.18 $ 7.00
Range of exercise prices, Granted lower limit $ 17.67 $ 19.73 $ 7.5
Range of exercise prices, Granted upper limit $ 24.64 $ 29.50 $ 27.18
Range of exercise prices Exercised, lower limit $ 0.91 $ 0.91 $ 2.00
Range of exercise prices Exercised, upper limit $ 27.18 $ 27.18 $ 9.00
Range of exercise prices Forfeited/cancelled, lower limit $ 0.94 $ 4.28 $ 2.00
Range of exercise prices Forfeited/cancelled, upper limit $ 29.50 $ 29.50 $ 27.18
Range of exercise prices Expired, lower limit $ 0.94 $ 4.28  
Range of exercise prices Expired, upper limit $ 27.18 $ 6.00  
Range of exercise prices Ending Balance, lower limit $ 0.91 $ 0.91 $ 2.00
Range of exercise prices Ending Balance, upper limit $ 29.50 $ 29.50 $ 27.18
Weighted-Average Exercise Price      
Beginning Balance $ 9.95 $ 6.05 $ 4.33
Granted $ 20.09 $ 24.09 $ 10.68
Assumed MTS Plan   $ 4.39  
Exercised $ 5.05 $ 4.07 $ 3.09
Forfeited/cancelled $ 17.04 $ 12.94 $ 6.21
Expired $ 2.73 $ 5.26  
Ending Balance $ 13.97 $ 9.95 $ 6.05
MTS
     
Number of Shares      
Range of exercise prices, Granted lower limit   $ 0.91  
Range of exercise prices, Granted upper limit   $ 23.29