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Equity Incentive Plans - Additional Information (Details) (USD $)
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3 Months Ended | 9 Months Ended | 12 Months Ended | 2 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended | 9 Months Ended | |||||||||||||||||||||||||
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Sep. 30, 2013
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Sep. 30, 2012
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Sep. 30, 2013
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Sep. 30, 2012
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Dec. 31, 2012
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Dec. 31, 2011
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Dec. 31, 2010
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Dec. 31, 2011
Shares Available For Grant
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Sep. 30, 2013
Shares Available For Grant
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Dec. 31, 2012
Shares Available For Grant
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Dec. 31, 2010
Shares Available For Grant
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Dec. 31, 2009
Shares Available For Grant
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Mar. 01, 2013
RSUs
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Sep. 30, 2013
RSUs
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Sep. 30, 2012
RSUs
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Sep. 30, 2013
RSUs
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Sep. 30, 2012
RSUs
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Dec. 31, 2012
RSUs
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Dec. 31, 2011
RSUs
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Sep. 30, 2013
Stock Options
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Sep. 30, 2012
Stock Options
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Sep. 30, 2013
Stock Options
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Sep. 30, 2012
Stock Options
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Dec. 31, 2012
Stock Options
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Dec. 31, 2011
Stock Options
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Dec. 31, 2010
Stock Options
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Sep. 30, 2013
Restricted Stock
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Sep. 30, 2012
Restricted Stock
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Sep. 30, 2013
Restricted Stock
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Sep. 30, 2012
Restricted Stock
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Dec. 31, 2012
Restricted Stock
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Dec. 31, 2011
Restricted Stock
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Dec. 31, 2010
Restricted Stock
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Sep. 30, 2013
Replacement Performance Shares
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Sep. 30, 2013
New Performance Shares
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Sep. 30, 2013
Performance Shares
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Sep. 30, 2013
Performance Shares
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Dec. 31, 2012
1998 Equity Incentive Plan
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Dec. 31, 2011
1998 Equity Incentive Plan
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Dec. 31, 2012
Common Stock
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Sep. 30, 2013
Maximum
RSUs
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Sep. 30, 2013
Maximum
Stock Options
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Sep. 30, 2013
Maximum
Restricted Stock
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| Share-based Compensation Arrangement by Share-based Payment Award | |||||||||||||||||||||||||||||||||||||||||||
| Increase in shares available for issuance under the Equity Incentive Plan | 12,800,000 | 1,088,834 | 12,800,000 | ||||||||||||||||||||||||||||||||||||||||
| Total shares approved under the Equity Incentive Plan | 69,900,000 | ||||||||||||||||||||||||||||||||||||||||||
| Shares available for issuance under the Equity Incentive Plan | 15,752,370 | 13,896,794 | 14,643,932 | 4,280,180 | 7,285,606 | ||||||||||||||||||||||||||||||||||||||
| Vesting period | 5 years | 5 years | 5 years | 6 months | 6 months | 5 years | 5 years | 5 years | |||||||||||||||||||||||||||||||||||
| Number of shares that RSUs convert into on the applicable vesting date | 1 | 1 | |||||||||||||||||||||||||||||||||||||||||
| Stock options expiration period | 10 years | 10 years | |||||||||||||||||||||||||||||||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period | 97,254 | 119,422 | 44,904 | 671,400 | |||||||||||||||||||||||||||||||||||||||
| Exercise price adjustment resulting from stock split | 50.00% | ||||||||||||||||||||||||||||||||||||||||||
| RSUs granted (shares) | 594,700 | 924,312 | 1,504,410 | 1,643,348 | 671,400 | 275,400 | 946,800 | ||||||||||||||||||||||||||||||||||||
| Performance Period (Duration) | 5 years | ||||||||||||||||||||||||||||||||||||||||||
| Closing stock price | $ 21.10 | ||||||||||||||||||||||||||||||||||||||||||
| Outstanding RSUs or restricted stock, intrinsic value | $ 49,600,000 | $ 2,400,000 | |||||||||||||||||||||||||||||||||||||||||
| Outstanding stock options, intrinsic value | 132,800,000 | ||||||||||||||||||||||||||||||||||||||||||
| Exercisable stock options, intrinsic value | 102,300,000 | ||||||||||||||||||||||||||||||||||||||||||
| Forfeiture rates used for grants to employees | 10.00% | 10.00% | 9.00% | ||||||||||||||||||||||||||||||||||||||||
| Forfeiture rates used for grants to non-employee directors and executive officers | 0.00% | 0.00% | 0.00% | ||||||||||||||||||||||||||||||||||||||||
| Fair value of RSUs or restricted stock vested during the period | 14,300,000 | 7,800,000 | 2,200,000 | 1,600,000 | 1,100,000 | 1,000,000 | |||||||||||||||||||||||||||||||||||||
| Period of time as a public company | 6 years | ||||||||||||||||||||||||||||||||||||||||||
| Number of coupon issues related to the risk-free rate | 0 | ||||||||||||||||||||||||||||||||||||||||||
| Dividend Yield | 0.00% | ||||||||||||||||||||||||||||||||||||||||||
| Fair value of stock options vested | 7,200,000 | 8,600,000 | 7,700,000 | ||||||||||||||||||||||||||||||||||||||||
| Intrinsic value of stock options exercised | 45,300,000 | 24,800,000 | 43,200,000 | ||||||||||||||||||||||||||||||||||||||||
| Stock-based compensation expense | 5,730,000 | 3,998,000 | 16,292,000 | 11,976,000 | 15,634,000 | 13,107,000 | 9,974,000 | 4,559,000 | 2,048,000 | 12,674,000 | 6,131,000 | 8,411,000 | 3,666,000 | 1,124,000 | 1,720,000 | 3,457,000 | 5,162,000 | 6,310,000 | 8,129,000 | 8,771,000 | 47,000 | 230,000 | 161,000 | 683,000 | 913,000 | 913,000 | 913,000 | 2,300,000 | 6,000,000 | ||||||||||||||
| Unrecognized Stock Based Compensation Expense Expected To Be Recognize In Current Year | $ 5,629,000 | $ 5,629,000 | $ 4,459,000 | $ 4,459,000 | $ 1,123,000 | $ 1,123,000 | $ 47,000 | $ 47,000 | $ 2,300,000 | $ 2,300,000 | |||||||||||||||||||||||||||||||||