Commitments and Contingencies Commitments and Contingencies (Narrative) $ in Millions	6 Months Ended
	Jun. 30, 2016 USD ($)
Loss Contingencies [Line Items]
Letters of Credit Outstanding, Amount	$ 1.5
Investment in development or redevelopment projects	110.1
Development/Redevelopment Obligation, Amount	137.1
Other Significant Project Obligations, Amount	$ 15.1
Minimum [Member]
Loss Contingencies [Line Items]
Development/Redevelopment Period	2 years
Minimum [Member] | Capital Addition Purchase Commitments [Member]
Loss Contingencies [Line Items]
Long-term Purchase Commitment, Period	1 year
Maximum [Member]
Loss Contingencies [Line Items]
Development/Redevelopment Period	3 years
Maximum [Member] | Capital Addition Purchase Commitments [Member]
Loss Contingencies [Line Items]
Long-term Purchase Commitment, Period	2 years