Equity (Details) (USD $) In Thousands, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 Y	Dec. 31, 2010 Y	Dec. 31, 2009 Y	Dec. 31, 2008 Y
Stock option activity
Options outstanding at the beginning of the period (in shares)	12,706,324	12,704,303	11,229,837
Options granted (in shares)	2,551,350	2,602,500	3,736,500
Options exercised (in shares)	(1,037,674)	(2,331,429)	(2,029,874)
Options forfeited (in shares)	(203,100)	(269,050)	(232,160)
Options outstanding at the end of the period (in shares)	14,016,900	12,706,324	12,704,303
Vested and non-vested expected to vest at the end of the period (in shares)	13,066,583
Exercisable at the end of the period (in shares)	6,380,324
Weighted Average Exercise Price
Weighted average exercise price, options outstanding at the beginning of the period (in dollars per share)	$ 33.93	$ 29.58	$ 25.82
Weighted average exercise price, options granted (in dollars per share)	$ 53.45	$ 43.00	$ 32.01
Weighted average exercise price, options exercised (in dollars per share)	$ 25.14	$ 19.99	$ 12.55
Weighted average exercise price, options forfeited (in dollars per share)	$ 39.75	$ 37.18	$ 35.89
Weighted average exercise price, options outstanding at the end of the period (in dollars per share)	$ 38.00	$ 33.93	$ 29.58
Weighted average exercise price, vested and non-vested expected to vest (in dollars per share)	$ 37.57
Weighted average exercise price, exercisable (in dollars per share)	$ 31.48
Weighted Average Remaining Contractual Term
Weighted average remaining contractual term of options outstanding (in years)	6.89	7.18	7.16	6.69
Weighted average remaining contractual term of options vested and non-vested expected to vest (in years)	6.79
Weighted average remaining contractual term of options exercisable (in years)	5.41
Aggregate Intrinsic Value
Aggregate intrinsic value of options outstanding (in dollars)	$ 125,067
Aggregate intrinsic value of options, vested and non-vested expected to vest (in dollars)	120,850
Aggregate intrinsic value of options exercisable (in dollars)	89,316
Status of the Company's non-vested options and changes during the year
Non-vested options at the beginning of the period (in shares)	7,623,976
Non-vested options, options granted (in shares)	2,551,350
Non-vested options, options vested (in shares)	(2,335,650)
Non-vested options, options forfeited (in shares)	(203,100)
Non-vested options at the end of the period (in shares)	7,636,576	7,623,976
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)	$ 12.78
Weighted average fair value at grant date, options granted (in dollars per share)	$ 14.19	$ 14.69	$ 11.12
Weighted average fair value at grant date, options vested (in dollars per share)	$ 12.23
Weighted average fair value at grant date, options forfeited (in dollars per share)	$ 13.00
Weighted average fair value at the grant date, options outstanding at the end of the period (in dollars per share)	$ 13.41	$ 12.78
Total intrinsic value of stock options exercised (in dollars)	29,697	67,841	56,900
Total fair value of stock options vested (in dollars)	28,563	23,714	17,360
Total compensation cost related to non-vested options not yet recognized (in dollars)	$ 74,434
Weighted average expected amortization period (in years)	3.26
2009 Option Plan
Share-based Compensation Arrangement by Share-based Payment Award
Shares available for the granting of additional stock options (in shares)	7,684,550,000
2000 Option Plan and 2009 Option Plan
Share-based Compensation Arrangement by Share-based Payment Award
Options ratable vesting period (in years)	5 years
Options exercisable period (in years)	10 years
Directors Option Plan
Share-based Compensation Arrangement by Share-based Payment Award
Shares available for the granting of additional stock options (in shares)	80,000
Options ratable vesting period (in years)	3 years
Options exercisable period (in years)	10 years