Stock-Based Compensation (Details) (USD $) | 3 Months Ended | 9 Months Ended | 3 Months Ended | 9 Months Ended | 18 Months Ended | 3 Months Ended | 9 Months Ended | 12 Months Ended | | 9 Months Ended | |
In Thousands, except Share data, unless otherwise specified | Sep. 30, 2013 | Sep. 30, 2012 | Sep. 30, 2013 | Sep. 30, 2012 | Jun. 30, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Sep. 30, 2013 | Jun. 30, 2013 | Mar. 31, 2013 | Sep. 30, 2012 | Sep. 30, 2013 | Sep. 30, 2012 | Dec. 31, 2012 | Sep. 30, 2013 | Sep. 30, 2013 | Sep. 30, 2013 | Sep. 30, 2013 | Sep. 30, 2013 |
| Restricted Shares | Restricted Shares | Restricted Shares | Stock Options | Stock Options | Stock Options | Stock Options | Stock Options | Stock Options | Stock Options | 2009 Employee Option Plan | 2000 Employee Option Plan and 2009 Employee Option Plan | 2004 Directors Option Plan | 2012 Directors Restricted Stock Plan | 2000 Employee Option Plan |
Share-based Compensation Arrangement by Share-based Payment Award | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Number of additional stock options that can be granted | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | 0 |
Shares available for the granting of additional stock options | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | 2,315,070 | ' | 70,000 | 95,131 | ' |
Options ratable vesting period | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | '5 years | '3 years | ' | ' |
Options exercisable period | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | '10 years | '10 years | ' | ' |
Number of additional stock options expected to be granted | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | 0 | ' | ' |
Expense incurred for stock-based compensation plans (in dollars) | $9,413 | $8,066 | $26,584 | $23,167 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Expense incurred for stock-based compensation plans, net of tax (in dollars) | 6,940 | 5,885 | 19,432 | 16,542 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Stock option activity | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Options outstanding at the beginning of the period (in shares) | ' | ' | ' | ' | ' | ' | ' | 14,198,590 | 12,344,775 | 13,446,719 | ' | 13,446,719 | ' | ' | ' | ' | ' | ' | ' |
Options granted (in shares) | ' | ' | ' | ' | ' | ' | ' | 40,850 | 2,742,150 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Options exercised (in shares) | ' | ' | ' | ' | ' | ' | ' | -378,310 | -843,615 | -1,043,444 | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Options forfeited (in shares) | ' | ' | ' | ' | ' | ' | ' | -26,980 | -44,720 | -58,500 | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Options outstanding at the end of the period (in shares) | ' | ' | ' | ' | ' | ' | ' | 13,834,150 | 14,198,590 | 12,344,775 | ' | 13,834,150 | ' | 13,446,719 | ' | ' | ' | ' | ' |
Vested and non-vested expected to vest at the end of the period (in shares) | ' | ' | ' | ' | ' | ' | ' | 12,497,070 | ' | ' | ' | 12,497,070 | ' | ' | ' | ' | ' | ' | ' |
Exercisable at the end of the period (in shares) | ' | ' | ' | ' | ' | ' | ' | 5,768,549 | ' | ' | ' | 5,768,549 | ' | ' | ' | ' | ' | ' | ' |
Weighted Average Exercise Price | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Weighted average exercise price, options outstanding at the beginning of the period (in dollars per share) | ' | ' | ' | ' | ' | ' | ' | $51.23 | $44.37 | $43.39 | ' | $43.39 | ' | ' | ' | ' | ' | ' | ' |
Weighted average exercise price, options granted (in dollars per share) | ' | ' | ' | ' | ' | ' | ' | $76.77 | $78 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Weighted average exercise price, options exercised (in dollars per share) | ' | ' | ' | ' | ' | ' | ' | $39.63 | $38.03 | $31.30 | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Weighted average exercise price, options forfeited (in dollars per share) | ' | ' | ' | ' | ' | ' | ' | $57.17 | $48.69 | $50.58 | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Weighted average exercise price, options outstanding at the end of the period (in dollars per share) | ' | ' | ' | ' | ' | ' | ' | $51.61 | $51.23 | $44.37 | ' | $51.61 | ' | $43.39 | ' | ' | ' | ' | ' |
Weighted average exercise price, vested and non-vested expected to vest (in dollars per share) | ' | ' | ' | ' | ' | ' | ' | $51.02 | ' | ' | ' | $51.02 | ' | ' | ' | ' | ' | ' | ' |
Weighted average exercise price, exercisable (in dollars per share) | ' | ' | ' | ' | ' | ' | ' | $41.28 | ' | ' | ' | $41.28 | ' | ' | ' | ' | ' | ' | ' |
Weighted Average Remaining Contractual Term | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Weighted average remaining contractual term of options outstanding | ' | ' | ' | ' | ' | ' | ' | '7 years 3 months 14 days | '7 years 5 months 26 days | '7 years 22 days | ' | ' | ' | '7 years 29 days | ' | ' | ' | ' | ' |
Weighted average remaining contractual term of options vested and non-vested expected to vest | ' | ' | ' | ' | ' | ' | ' | '7 years 2 months 12 days | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Weighted average remaining contractual term of options exercisable | ' | ' | ' | ' | ' | ' | ' | '5 years 9 months 18 days | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Aggregate Intrinsic Value | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Aggregate intrinsic value of options outstanding (in dollars) | ' | ' | ' | ' | ' | ' | ' | 358,182 | 379,390 | 373,596 | ' | 358,182 | ' | 268,596 | ' | ' | ' | ' | ' |
Aggregate intrinsic value of options, vested and non-vested expected to vest (in dollars) | ' | ' | ' | ' | ' | ' | ' | 330,899 | ' | ' | ' | 330,899 | ' | ' | ' | ' | ' | ' | ' |
Aggregate intrinsic value of options exercisable (in dollars) | ' | ' | ' | ' | ' | ' | ' | 208,247 | ' | ' | ' | 208,247 | ' | ' | ' | ' | ' | ' | ' |
Status of the Company's non-vested options and changes during the year | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Non-vested options at the beginning of the period (in shares) | ' | ' | ' | ' | ' | ' | ' | 8,054,931 | 7,884,057 | 7,951,177 | ' | 7,951,177 | ' | ' | ' | ' | ' | ' | ' |
Non-vested options, options granted (in shares) | ' | ' | ' | ' | ' | ' | ' | 40,850 | 2,742,150 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Non-vested options, options vested (in shares) | ' | ' | ' | ' | ' | ' | ' | -3,200 | -2,526,556 | -8,620 | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Non-vested options, options forfeited (in shares) | ' | ' | ' | ' | ' | ' | ' | -26,980 | -44,720 | -58,500 | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Non-vested options at the end of the period (in shares) | ' | ' | ' | ' | ' | ' | ' | 8,065,601 | 8,054,931 | 7,884,057 | ' | 8,065,601 | ' | 7,951,177 | ' | ' | ' | ' | ' |
Weighted Average Fair Value at Grant Date | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Weighted average fair value at the grant date, options outstanding at the beginning of the period (in dollars per share) | ' | ' | ' | ' | ' | ' | ' | $14.75 | $13.35 | $13.36 | ' | $13.36 | ' | ' | ' | ' | ' | ' | ' |
Weighted average fair value at grant date, options granted (in dollars per share) | ' | ' | ' | ' | ' | ' | ' | $17.97 | $17.41 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Weighted average fair value at grant date, options vested (in dollars per share) | ' | ' | ' | ' | ' | ' | ' | $14.97 | $13.32 | $15.62 | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Weighted average fair value at grant date, options forfeited (in dollars per share) | ' | ' | ' | ' | ' | ' | ' | $14.24 | $13.40 | $13.50 | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share) | ' | ' | ' | ' | ' | ' | ' | $14.76 | $14.75 | $13.35 | ' | $14.76 | ' | $13.36 | ' | ' | ' | ' | ' |
Total intrinsic value of stock options exercised (in dollars) | ' | ' | ' | ' | ' | ' | ' | 16,456 | ' | ' | 36,383 | 91,091 | 77,320 | ' | ' | ' | ' | ' | ' |
Total fair value of stock options vested (in dollars) | ' | ' | ' | ' | ' | ' | ' | 49 | ' | ' | 41 | 33,830 | 30,922 | ' | ' | ' | ' | ' | ' |
Total compensation cost related to non-vested options not yet recognized (in dollars) | ' | ' | ' | ' | ' | ' | ' | 92,718 | ' | ' | ' | 92,718 | ' | ' | ' | ' | ' | ' | ' |
Weighted average expected amortization period | ' | ' | ' | ' | ' | '7 months 24 days | ' | ' | ' | ' | ' | '3 years 6 months 7 days | ' | ' | ' | ' | ' | ' | ' |
Number of restricted shares issued | ' | ' | ' | ' | 12,824 | ' | 17,045 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Weighted-average grant date fair value of restricted shares (in dollars per share) | ' | ' | ' | ' | $78 | ' | $53.78 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |
Total compensation cost related to non-vested restricted shares not yet recognized (in dollars) | ' | ' | ' | ' | ' | $645 | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' | ' |