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Summary of Transactions in Stock-Based Compensation Plans (Details) (USD $)
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9 Months Ended | 12 Months Ended | 2 Months Ended | 9 Months Ended | 12 Months Ended | 9 Months Ended | 12 Months Ended | 9 Months Ended | 12 Months Ended | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
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Dec. 31, 2012
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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, 2011
Shares Available For Grant
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Dec. 31, 2010
Shares Available For Grant
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Mar. 01, 2013
RSUs
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Sep. 30, 2013
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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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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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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| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Including Options, Shares Available for Grant [Roll Forward] | |||||||||||||||||
| Balance, beginning of period | 14,643,932 | 15,752,370 | 4,280,180 | 7,285,606 | |||||||||||||
| Granted | (924,312) | (1,504,410) | (1,643,348) | (3,423,066) | |||||||||||||
| Shares issued for director compensation | (31,166) | ||||||||||||||||
| Cancelled | 177,174 | 395,972 | 346,704 | 417,640 | |||||||||||||
| Additional shares authorized | 12,800,000 | ||||||||||||||||
| Balance, end of period | 13,896,794 | 14,643,932 | 15,752,370 | 4,280,180 | |||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] | |||||||||||||||||
| Balance, beginning of period | 9,355,070 | 9,355,070 | 13,078,092 | 16,147,930 | 18,658,814 | ||||||||||||
| Granted | 3,423,066 | ||||||||||||||||
| Exercised | (2,143,544) | (3,446,472) | (2,768,038) | (5,516,310) | |||||||||||||
| Cancelled | (79,920) | (276,550) | (301,800) | (417,640) | |||||||||||||
| Balance, end of period | 9,355,070 | 7,131,606 | 9,355,070 | 13,078,092 | 16,147,930 | ||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Roll Forward] | |||||||||||||||||
| Balance, weighted average exercise price, beginning of period | $ 6.90 | $ 6.90 | $ 6.47 | $ 6.14 | $ 4.41 | ||||||||||||
| Granted, weighted average exercise price | $ 9.98 | ||||||||||||||||
| Exercised, weighted average exercise price | $ 6.37 | $ 5.13 | $ 4.31 | $ 2.53 | |||||||||||||
| Cancelled, weighted average exercise price | $ 8.80 | $ 8.30 | $ 8.44 | $ 8.06 | |||||||||||||
| Balance, weighted average exercise price, end of period | $ 6.90 | $ 7.04 | $ 6.90 | $ 6.47 | $ 6.14 | ||||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Roll Forward] | |||||||||||||||||
| Balance, weighted average grant date fair value, beginning of period | $ 14.02 | $ 14.02 | $ 11.80 | $ 9.47 | $ 9.49 | $ 9.50 | $ 9.50 | ||||||||||
| Granted, weighted average grant date fair value | $ 22.18 | $ 15.86 | $ 11.80 | ||||||||||||||
| Vested, weighted average grant date fair value | $ 15.04 | $ 13.09 | $ 11.84 | $ 9.54 | $ 9.51 | $ 9.51 | $ 9.51 | ||||||||||
| Cancelled, weighted average grant date fair value | $ 16.14 | $ 14.03 | $ 11.77 | ||||||||||||||
| Balance, weighted average grant date fair value, end of period | $ 16.63 | $ 14.02 | $ 11.80 | $ 9.30 | $ 9.47 | $ 9.49 | $ 9.50 | ||||||||||
| Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] | |||||||||||||||||
| Balance, beginning of period | 2,351,362 | 2,351,362 | 1,433,582 | 116,000 | 212,000 | 308,000 | 404,000 | ||||||||||
| Granted | 594,700 | 924,312 | 1,504,410 | 1,643,348 | |||||||||||||
| Vested | (593,671) | (467,208) | (164,862) | (86,000) | (96,000) | (96,000) | (96,000) | ||||||||||
| Cancelled | (97,254) | (119,422) | (44,904) | ||||||||||||||
| Balance, end of period | 2,584,749 | 2,351,362 | 1,433,582 | 30,000 | 116,000 | 212,000 | 308,000 | ||||||||||