Equity Incentive Compensation Plans (Stock Options) (Details) (USD $)	1 Months Ended		3 Months Ended
	Mar. 31, 2012		Mar. 31, 2012 year
Stock options activity
Outstanding at the beginning of the period (in shares)			1,520,689
Granted (in shares)	82,262
Exercised (in shares)			(197,209)
Cancelled/expired (in shares)			0
Outstanding at the end of the period (in shares)	1,405,742		1,405,742
Stock options, Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)			$ 30.32
Granted (in dollars per share)	$ 53.02		$ 53.02
Exercised (in dollars per share)	$ 17.73		$ 17.73
Cancelled/expired (in dollars per share)			$ 0.00
Outstanding at the end of the period (in dollars per share)	$ 33.41		$ 33.41
Stock options, Aggregate Intrinsic Value
Outstanding at the beginning of the period			$ 17,798,000	[1]
Exercised			6,779,000	[1]
Outstanding at the end of the period	20,317,000	[1]	20,317,000	[1]
Stock options, Number of Shares Exercisable
Options outstanding at the beginning of the period (in shares)			1,434,020
Options outstanding at the end of the period (in shares)	1,257,883		1,257,883
Fair value assumptions
Expected volatility (as a percent)			50.00%
Risk-free interest rate (as a percent)			0.95%
Dividend yield (as a percent)			0.57%
Expected term (in years)			5.2
Total unrecognized compensation cost	$ 3,200,000		$ 3,200,000
Vesting period (in years)			4 years
Anniversary date through which options are exercisable from grant date			Tenth Year
Period of recognition of unrecognized compensation cost (in years)			4.0

[1] The intrinsic value of a stock option is the amount by which the market value of the underlying stock at the end of the related period exceeds the exercise price of the option.