Unaudited Condensed Consolidated Statements of Cash Flows (Parenthetical) - USD ($) $ in Millions	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015
Unaudited Condensed Consolidated Statements of Cash Flows
Interest capitalized	$ 21.8	$ 15.9

The amount of cash paid during the current period for interest that is capitalized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 13
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=56944662&loc=d3e3213-108585

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