Statements of Cash Flow (Details) - USD ($)	3 Months Ended
Mar. 31, 2016	Mar. 31, 2015
Supplemental Cash Flow Information [Abstract]
Interest payments	$ 56,968,000	$ 56,632,000
Income taxes paid	$ 5,644,000	$ 4,769,000

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=56944662&loc=d3e3536-108585

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