Noncontrolling Interests Redeemable interest in property partnership (Narrative) (Details) - Fountain Square [Member] - USD ($) $ in Millions	Sep. 15, 2015	Aug. 06, 2015	Oct. 04, 2012
Noncontrolling Interest [Line Items]
Aggregate purchase price			$ 385.0
Indebtedness assumed			$ 211.3
Ownership Percentage	50.00%	50.00%	50.00%
Fixed Price to Acquire Remaining Portion of Joint venture		$ 100.9
Payments to Acquire Businesses, Gross			$ 87.0
Ownership Percentage by the Company			50.00%
Future Fixed Price to Acquire Remaining Portion of Joint venture			$ 102.0
Fixed Price Option Expiration Date			Jan. 31, 2016
Payments for Repurchase of Redeemable Noncontrolling Interest	$ 100.9
Mortgage debt assumed upon acquisition of noncontrolling interest	$ 105.6