Equity Incentive Compensation Plans (Stock Options) (Details) (USD $)	12 Months Ended						1 Months Ended
	Dec. 31, 2011 year		Dec. 31, 2010		Dec. 31, 2009		Mar. 31, 2011 Executive officers and other officers
Stock options activity
Outstanding at the beginning of the period (in shares)	2,017,225		2,276,020		2,421,650
Granted (in shares)	89,865		0		0		89,865
Exercised (in shares)	(579,635)		(227,100)		(62,050)
Cancelled/expired (in shares)	(6,765)		(31,695)		(83,580)
Outstanding at the end of the period (in shares)	1,520,690		2,017,225		2,276,020
Stock options, Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)	$ 25.87		$ 25.36		$ 25.16
Granted (in dollars per share)	$ 48.50		$ 0.00		$ 0.00
Exercised (in dollars per share)	$ 17.47		$ 19.40		$ 13.52
Cancelled/expired (in dollars per share)	$ 45.92		$ 35.51		$ 28.48
Outstanding at the end of the period (in dollars per share)	$ 30.32		$ 25.87		$ 25.36
Stock options, Aggregate Intrinsic Value
Outstanding at the beginning of the period	$ 35,974,000	[1]	$ 15,296,000	[1]	$ 0	[1]
Exercised	17,746,000	[1]	3,570,000	[1]	560,000	[1]
Outstanding at the end of the period	17,798,000	[1]	35,974,000	[1]	15,296,000	[1]
Stock options, Number of Shares Exercisable
Options outstanding at the beginning of the period (in shares)	1,884,937		2,008,325		1,842,532
Options outstanding at the end of the period (in shares)	1,434,020		1,884,937		2,008,325
Vesting period (in years)	4 years
Anniversary date through which options are exercisable from grant date	Tenth
Fair value assumptions
Expected volatility (as a percent)	45.00%
Risk-free interest rate (as a percent)	2.54%
Dividend yield (as a percent)	0.62%
Expected term (in years)	6.0
Total unrecognized compensation cost	$ 1,300,000
Period of recognition of unrecognized compensation cost (in years)	3.25

[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.