Equity Incentive Compensation Plans (Stock Options) (Details) (USD $)	0 Months Ended	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2012	Dec. 31, 2011		Dec. 31, 2010
Equity Incentive Compensation Plans
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Exercise Price	$ 31.65	$ 31.65
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Outstanding Options, Weighted Average Remaining Contractual Term		4 years 29 days
Stock options activity
Outstanding at the beginning of the period (in shares)		1,520,689	2,017,225		2,276,020
Granted (in shares)		82,262	89,865		0
Exercised (in shares)		(215,359)	(579,636)		(227,100)
Canceled/expired		0	(6,765)		(31,695)
Outstanding at the end of the period (in shares)	1,387,592	1,387,592	1,520,689		2,017,225
Stock options, Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share)		$ 30.32	$ 25.87		$ 25.36
Granted (in dollars per share)		$ 53.02	$ 48.50		$ 0.00
Exercised (in dollars per share)		$ 17.12	$ 17.47		$ 19.40
Cancelled/expired (in dollars per share)		$ 0.00	$ 45.92		$ 35.51
Outstanding at the end of the period (in dollars per share)	$ 33.71	$ 33.71	$ 30.32		$ 25.87
Stock options, Aggregate Intrinsic Value
Exercised		$ 7,194,000	$ 17,746,000	[1]	$ 3,570,000	[1]
Outstanding at the end of the period	4,681,000	4,681,000
Stock options, Number of Shares Exercisable
Options outstanding at the end of the period (in shares)	1,239,733	1,239,733
Vesting period (in years)		4 years
Anniversary date through which options are exercisable from grant date		Tenth Year
Fair value assumptions
Expected volatility (as a percent)		50.00%	45.00%
Risk-free interest rate (as a percent)		0.95%	2.54%
Dividend yield (as a percent)		0.57%	0.62%
Expected term (in years)		5 years 2 months	6 years
Total unrecognized compensation cost	2,500,000	2,500,000
Period of recognition of unrecognized compensation cost (in years)	3 years 3 months
Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Intrinsic Value	4,681,000	4,681,000
Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Exercisable Options, Weighted Average Remaining Contractual Term		3 years 6 months 12 days
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	1,383,702	1,383,702
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Weighted Average Exercise Price	$ 33.66	$ 33.66
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Aggregate Intrinsic Value	$ 4,681,000	$ 4,681,000
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Exercisable, Weighted Average Remaining Contractual Term		4 years 26 days

[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.