Stock Based Compensation (Details) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Assumptions Used in Fair Value Calculation of Stock Options (Table Details) [Abstract]
Risk free interest rate, minimum	0.12%	0.12%	0.26%
Risk free interest rate, maximum	1.78%	1.78%	2.16%
Risk free interest rate, weighted average	0.71%	0.71%	1.01%
Expected dividend yield, minimum	0.90%	0.70%
Expected dividend yield, maximum	2.30%	2.30%	0.80%
Expected dividend yield, weighted average	1.31%	1.31%
Expected life (in years)	6 years 0 months 18 days	6 years 0 months 18 days	5 years 5 months 23 days
Expected volatility, minimum	35.42%	33.42%	34.95%
Expected volatility, maximum	50.12%	50.12%	56.30%
Expected volatility, weighted average	42.48%	42.48%	47.87%
Forfeiture rate, minimum	7.55%	7.55%	5.00%
Forfeiture rate, maximum	13.41%	13.41%	15.43%
Forfeiture rate, weighted average	9.48%	9.48%	10.18%
Employee stock options granted	733,297	733,297	796,345
Weighted average grant date fair value	$ 10.07	$ 7.50	$ 6.00
Restricted Stock Unit Activity (Table Details) [Abstract]
Number of nonvested restricted stock units outstanding	440,185	458,809
Granted	212,067
Vested	(126,737)
Forfeited	(103,954)
Weighted average grant date fair value, outstanding	$ 28.96	$ 21.09
Weighted average grant date fair value, granted	$ 35.43
Weighted average grant date fair value, vested	$ 18.23
Weighted average grant date fair value, forfeited	$ 17.64
Stock Option Activity (Table Details) [Abstract]
Number of awards outstanding	2,260,410	2,431,180
Granted	733,297	733,297	796,345
Exercised	(606,909)
Forfeited	(297,158)
Exercisable	906,583
Weighted Average Exercise Price [Abstract]
Equity awards outstanding	$ 28.57	$ 24.72
Granted	$ 36.60
Exercised	$ 23.27
Forfeited	$ 27.75
Exercisable	$ 24.31
Weighted Average Remaining Contractual Life [Abstract]
Equity awards outstanding	7 years 0 months 4 days
Exercisable	4 years 9 months 0 days
Aggregate Intrinsic Value [Abstract]
Equity awards outstanding	$ 13,623,000
Exercised	7,500,000	24,100,000	9,100,000
Exercisable	8,529,000
Stock-Based Compensation (Details) [Line Items]
Number of awards outstanding	2,260,410	2,431,180
Tax benefits from stock option exercises	4,348,000	7,036,000	2,974,000
Stock-based compensation expense	8,366,000	4,471,000	4,123,000
Stock-based compensation expense, net of tax	5,300,000	2,800,000	2,600,000
Vesting % of performance based restricted stock units, maximum	200.00%
Exercise period of options once vested	10
Equity Awards under 2006 Plan [Member]
Stock Option Activity (Table Details) [Abstract]
Number of awards outstanding	1,616,983	1,610,262
Stock-Based Compensation (Details) [Line Items]
Number of shares authorized to issue	7,000,000
Number of awards outstanding	1,616,983	1,610,262
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	870,643	852,076
Stock-Based Compensation (Details) [Line Items]
Number of shares authorized to issue	2,468,461
Number of awards outstanding	870,643	852,076
Equity Awards under Prior Plan [Member]
Stock Option Activity (Table Details) [Abstract]
Number of awards outstanding	212,969	427,651
Stock-Based Compensation (Details) [Line Items]
Number of shares authorized to issue	14,562,865
Number of awards outstanding	212,969	427,651
Stock Options [Member]
Stock-Based Compensation (Details) [Line Items]
Unvested options- to result in compensation expense	8,800,000
Weighted average number of years to vesting	2 years 9 months 11 days
Restricted Stock Units (RSUs) [Member]
Stock-Based Compensation (Details) [Line Items]
Unvested options- to result in compensation expense	$ 5,200,000
Weighted average number of years to vesting	1 year 10 months 13 days
Minimum [Member]
Stock-Based Compensation (Details) [Line Items]
Vesting period of options granted	1 year
Maximum [Member]
Stock-Based Compensation (Details) [Line Items]
Vesting period of options granted	4 years