Stock Incentive Plans - Performance Share Plans (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Performance Share Plan Expense, Liability Portion					$ 19.6
Incremental modification expense	5.5		7.0
Performance Share Plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Awarding of performance shares earned payable in cash			40.00%
Awarding of performance shares earned payable in common stock			60.00%
Compensation expense recognized in cash by Company over the performance period			40.00%
Compensation expense recognized in common stock by Company over the performance period			60.00%
Performance share plan expense	$ 10.8		$ 35.5		$ 26.3
Performance share plan, shares issued in period	545,375	[1]	1,116,000	[1]	1,076,360	[1]

[1] Shares are issued in February of the following year.