Amount of contributions made to multiemployer plans by the employer. A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 11

-URI http://asc.fasb.org/extlink&oid=35742057&loc=SL14450702-114947

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 9

-URI http://asc.fasb.org/extlink&oid=35742057&loc=SL14450691-114947

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 715

-SubTopic 80

-Section 50

-Paragraph 5

-Subparagraph (e)(1)

-URI http://asc.fasb.org/extlink&oid=35742057&loc=SL14450657-114947

Name:	us-gaap_MultiemployerPlanPeriodContributions
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

Postretirement Benefit Plans (Details) (Multiemployer Health and Welfare Plan [Member], USD $)	5 Months Ended	7 Months Ended	12 Months Ended			24 Months Ended
	May 31, 2012	Dec. 31, 2014 employee	Dec. 31, 2014 employee	Dec. 31, 2013	Dec. 31, 2012	May 31, 2014
Multiemployer Health and Welfare Plan [Member]
Multiemployer Plans [Line Items]
Number of employees in plan		652	652
Required employer's contribution per hour per active employee	$ 5.50	$ 5.25				$ 5.00
Period Contributions			$ 7,300,000	$ 6,900,000	$ 6,700,000