General - General information (Details) - USD ($)	6 Months Ended
Jun. 30, 2016	Jun. 30, 2015
General
Decrease in other adjustments to reconcile net margin to net cash provided by operating activities	$ (3,429,000)	$ (3,312,000)
Decrease in cash paid for property additions	$ (301,545,000)	(239,510,000)
Adjustments
General
Decrease in other adjustments to reconcile net margin to net cash provided by operating activities		16,528,000
Decrease in cash paid for property additions		$ 16,528,000

The cash outflow for purchases of and capital improvements on property, plant and equipment (capital expenditures), software, and other intangible assets.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Investing Activities
-URI http://asc.fasb.org/extlink&oid=6516133

Reference 2: 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

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration