Indebtedness (Overview) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Debt Disclosure [Abstract]
Weighted average interest rate	4.30%	4.60%	5.00%
Interest costs capitalized	$ 24.1	$ 16.7	$ 13.2
Cash paid for interest	$ 142.7	$ 149.6	$ 164.9

The amount of cash paid for interest during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=6367179&loc=d3e4297-108586

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (e)
-URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3536-108585

Name:	us-gaap_InterestPaid
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration