Share-Based Compensation & Deferred Compensation Arrangements (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Total cost of share-based compensation	$ 5.8	$ 4.9	$ 4.6
Less capitalized cost	0.8	1.7	1.6
Total in other operating expense	5.0	3.2	3.0
Less income tax benefit in earnings	2.0	1.3	1.2
After tax effect of share-based compensation	3.0	1.9	1.8
Deferred Compensation Plans [Abstract]
Liability associated with deferred compensation plans	21.1	19.1
Portion of liability classified in Accrued liabilities	0.7	0.5
Impact of deferred compensation plans on Other operating expenses	2.1	2.3	0.8
Amount recorded in earnings related to the investment activities in phantom stock associated with deferred compensation plans	1.7	1.6	(1.5)
Cash surrender value of life insurance policies	27.3	27.5
Earnings from investments in corporate-owned life insurance policies	0.1	1.9	4.1
Restricted Stock and Restricted Stock Units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Vesting period for performance-based awards to executives and key non-officer employees (in years)	4
Vesting period for time-vested awards to non-officer employees (in years)	3
Vesting period for awards to non-employee directors (in years)	1
Performance Measurement Time Frame For Grants To Executives And Key Nonofficer Emplyees In Years	3
Share Based Payment Award Equity Instruments Other Than Options [Roll Forward]
Restricted awards at beginning of period (in shares)	668,892
Granted (in shares)	277,480
Vested (in shares)	(108,390)
Forfeited (in shares)	(139,872)
Restricted awards at end of period (in shares)	698,110
Weighted average grant date fair value at end of period (in dollars per share)	$ 30.23
Restricted Stock [Member]
Share Based Payment Award Equity Instruments Other Than Options [Roll Forward]
Restricted awards at beginning of period (in shares)	41,458
Granted (in shares)	27,518
Vested (in shares)	(7,226)
Forfeited (in shares)	(7,737)
Restricted awards at end of period (in shares)	54,013	41,458
Weighted average grant date fair value at beginning of period (in dollars per share)	$ 26.19
Weighted average grant date fair value of shares granted during period (in dollars per share)	$ 25.64
Weighted average grant date fair value of shares vested during period (in dollars per share)	$ 28.63
Weighted average grant date fair value of shares forfeited during period (in dollars per share)	$ 28.61
Weighted average grant date fair value at end of period (in dollars per share)	$ 25.22	$ 26.19
Total unrecognized compensation cost related to restricted stock awards	7.6
Weighted-average life of unrecognized compensation cost (in years)	1.6
Total fair value of liability awards vested	3.0	5.0	2.8
Total fair value of equity awards vested	0.2	0.2	0.1
Stock Options [Member]
Share Based Payment Award Equity Instruments Other Than Options [Roll Forward]
Length of continuous service required for option awards (in years)	3
Option awards term (in years)	10
Vesting period of option awards (in years)	3
Share Based Payment Award Options Outstanding [Roll Forward]
Outstanding at beginning of period (in shares)	929,806
Exercised (in shares)	(522,173)
Outstanding at end of period (in shares)	407,633	929,806
Exercisable at end of period (in shares)	407,633
Weighted average exercise price at beginning of period (in dollars per share)	$ 24.55
Weighted average exercise price of options exercised (in dollars per share)	$ 23.61
Weighted average exercise price at end of period (in dollars per share)	$ 25.74	$ 24.55
Weighted average exercise price of exercisable shares at end of period (in dollars per share)	$ 25.74
Remaining contractual term at end of period (in years)	2.5
Remaining contractual term of exercisable shares at end of period (in years)	2.5
Outstanding at end of period	1.8
Exercisable at end of period	1.8
Intrinsic value of options exercised	2.4	1.3
Tax benefit realized for tax deductions from option exercises	1.0	0.5
Cash received upon exercise of stock options	12.3	9.5
Stock repurchased during period	$ 12.8	$ 1.2