Stock Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Assumptions Used in Fair Value Calculation of Stock Options (Table Details) [Abstract]
Risk free interest rate, minimum	0.12%	0.26%	0.37%
Risk free interest rate, maximum	1.78%	2.16%	2.04%
Risk free interest rate, weighted average	0.71%	1.01%	1.10%
Expected life (in years)	6.05	5.48	5.34
Expected volatility, minimum	33.42%	34.95%	45.30%
Expected volatility, maximum	50.12%	56.30%	66.50%
Expected volatility, weighted average	42.48%	47.87%	55.08%
Forfeiture rate, minimum	7.55%	5.00%	3.64%
Forfeiture rate, maximum	13.41%	15.43%	24.80%
Forfeiture rate, weighted average	9.48%	10.18%	11.23%
Employee stock options granted	770,245	796,345	678,370
Weighted average grant date fair value	$ 7.50	$ 6.00	$ 5.72
Expected dividend yield, minimum	0.70%
Expected dividend yield, maximum	2.30%
Expected dividend yield, weighted average	1.31%
Expected dividend yield		0.80%
Restricted Stock Unit Activity (Table Details) [Abstract]
Number of nonvested restricted stock units outstanding	458,809	423,497
Granted	128,126
Vested	(40,578)
Forfeited	(52,236)
Weighted average grant date fair value, outstanding	$ 21.09	$ 17.52
Weighted average grant date fair value, granted	$ 30.08
Weighted average grant date fair value, vested	$ 16.89
Weighted average grant date fair value, forfeited	$ 17.42
Stock Option Activity (Table Details) [Abstract]
Number of awards outstanding	2,431,180	3,707,142
Granted	770,245	796,345	678,370
Exercised	(1,754,697)
Forfeited	(291,510)
Exercisable	1,127,188
Weighted Average Exercise Price [Abstract]
Equity awards outstanding	$ 24.72	$ 20.78
Granted	$ 30.60
Exercised	$ 19.35
Forfeited	$ 22.72
Exercisable	$ 24.01
Weighted Average Remaining Contractual Life [Abstract]
Equity awards outstanding	6.71
Exercisable	4.53
Aggregate Intrinsic Value [Abstract]
Equity awards outstanding	$ 29,898,000
Exercised	24,100,000	9,100,000	1,000,000
Exercisable	14,685,000
Stock-Based Compensation (Details) [Line Items]
Tax benefits from stock option exercises	7,036,000	2,974,000	270,000
Stock-based compensation expense, net of tax	2,800,000	2,600,000	2,300,000
Stock-based compensation expense	4,471,000	4,123,000	3,731,000
Vesting % of performance based restricted stock units, maximum	150.00%
Equity Awards under 2006 Plan [Member]
Stock Option Activity (Table Details) [Abstract]
Number of awards outstanding	1,610,262	1,796,575
Stock-Based Compensation (Details) [Line Items]
Number of shares authorized to issue	7,000,000
Restricted Stock under 2006 Plan [Member]
Stock-Based Compensation (Details) [Line Items]
Number of shares authorized to issue	3,500,000
Equity Awards under Equity Incentive Plan [Member]
Stock Option Activity (Table Details) [Abstract]
Number of awards outstanding	852,076	726,539
Stock-Based Compensation (Details) [Line Items]
Number of shares authorized to issue	2,468,461
Equity Awards under Prior Plan [Member]
Stock Option Activity (Table Details) [Abstract]
Number of awards outstanding	427,651	1,607,525
Stock-Based Compensation (Details) [Line Items]
Number of shares authorized to issue	14,562,865
Restricted Stock Units (RSUs) [Member]
Stock-Based Compensation (Details) [Line Items]
Unvested options- to result in compensation expense	2,400,000
Weighted average number of years to vesting	1.02
Stock Options [Member]
Stock-Based Compensation (Details) [Line Items]
Unvested options- to result in compensation expense	$ 7,300,000
Weighted average number of years to vesting	1.65