Financial Instruments - Fair Value Measurements (Details) - Fair Value Hierarchy [Domain] - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 2,525,114	$ 2,552,997
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-term debt	$ 2,821,080	$ 3,002,701

Fair value portion of debt instrument payable, including, but not limited to, notes payable and loans payable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13433-108611

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=35750535&loc=d3e13476-108611

Name:	us-gaap_DebtInstrumentFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant