General (Details 6) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Share-based compensation
Stock compensation expense	$ 4,365,000	$ 4,205,000	$ 9,467,000	$ 8,983,000
Estimated forfeitures (as a percent)		4.00%	4.00%
Benefits of tax deductions in excess of recognized stock compensation expenses			400,000	1,600,000
Change to additional paid in capital related to tax net benefits (deficiencies)			200,000	1,400,000
Deficiency of tax deductions offset by tax benefits in recognized stock compensation expenses			400,000	1,600,000
Benefit of tax deductions offset by tax deficiency in recognized stock compensation expenses			$ (200,000)	$ (200,000)
Stock options
Stock options, nonvested restricted stock awards and nonvested restricted stock units
Grants in period, weighted average grant date fair value (in dollars per share)	$ 11.80
Expected volatility (as a percent)	30.30%
Stock option activity
Outstanding, beginning of period (in shares)			3,841,233
Granted (in shares)			1,347,268
Forfeited (in shares)			(298,733)
Exercised (in shares)			(83,476)
Outstanding, end of period (in shares)	4,806,292		4,806,292
Vested and expected to vest end of period (in shares)	4,683,445		4,683,445
Exercisable, end of period (in shares)	2,527,059		2,527,059
Weighted average exercise price of stock options
Outstanding, beginning of period (in dollars per share)			$ 42.65
Granted (in dollars per share)	$ 47.47		$ 47.47
Forfeited (in dollars per share)	$ 45.27		$ 45.27
Exercised (in dollars per share)	$ 35.98		$ 35.98
Outstanding, end of period (in dollars per share)	$ 43.95		$ 43.95
Vested and expected to vest end of period (in dollars per share)	$ 43.86		$ 43.86
Exercisable, end of period (in dollars per share)	$ 40.84		$ 40.84
Tenure of award			P10Y
Additional disclosures
Vesting period			3 years
Nonvested restricted stock awards
Nonvested restricted stock awards and units
Outstanding, beginning of period (in shares)			18,748
Awarded (in shares)			23,672
Vested (in shares)			(18,748)
Outstanding, ending of period (in shares)	23,672		23,672
Weighted average exercise price of nonvested restricted stock award and units
Outstanding, beginning of period (in dollars per share)			$ 52.11
Awarded (in dollars per share)			$ 42.25
Vested (in dollars per share)			$ 52.11
Outstanding, ending of period (in dollars per share)	$ 42.25		$ 42.25
Additional disclosures
Vesting period			1 year
Nonvested restricted stock units
Nonvested restricted stock awards and units
Outstanding, beginning of period (in shares)			206,338
Awarded (in shares)			127,913
Vested (in shares)			(99,976)
Forfeited (in shares)			(24,302)
Outstanding, ending of period (in shares)	209,973		209,973
Weighted average exercise price of nonvested restricted stock award and units
Outstanding, beginning of period (in dollars per share)			$ 44.63
Awarded (in dollars per share)			$ 47.46
Vested (in dollars per share)			$ 41.81
Forfeited (in dollars per share)	$ 47.44		$ 47.44
Outstanding, ending of period (in dollars per share)	$ 47.36		$ 47.36
Additional disclosures
Vesting period			3 years