Basis of Presentation (New Accounting Pronouncement Early Adoption) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
New Accounting Pronouncement, Early Adoption [Line Items]
Other current assets	$ 8,966us-gaap_OtherAssetsCurrent	$ 9,285us-gaap_OtherAssetsCurrent
Revision of debt issuance costs	(51,209)us-gaap_UnamortizedDebtIssuanceExpense	(54,765)us-gaap_UnamortizedDebtIssuanceExpense
Other long-term assets	69,919us-gaap_OtherAssetsNoncurrent	67,748us-gaap_OtherAssetsNoncurrent
Long-term debt	0	3,068,878
New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncement, Early Adoption [Line Items]
Other current assets		9,285
Other long-term assets		67,748
Long-term debt		3,068,878
Other Current Assets \| New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncement, Early Adoption [Line Items]
Revision of debt issuance costs		(10,257)
Debt issuance cost, other long term assets \| New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncement, Early Adoption [Line Items]
Revision of debt issuance costs		(44,508)
Debt issuance cost, long term debt \| New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncement, Early Adoption [Line Items]
Revision of debt issuance costs		(54,765)
Prior to revision
New Accounting Pronouncement, Early Adoption [Line Items]
Other current assets		19,542
Other long-term assets		112,256
Long-term debt		$ 3,123,643

Amount of long-term debt and capital lease obligation due after one year or beyond the normal operating cycle, if longer.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.22)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 6

-Section H

+ Details

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

- Details

Name:	us-gaap_NewAccountingPronouncementEarlyAdoptionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Aggregate carrying amount, as of the balance sheet date, of current assets not separately disclosed in the balance sheet. Current assets are expected to be realized or consumed within one year (or the normal operating cycle, if longer).

+ References

+ Details

Name:	us-gaap_OtherAssetsCurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Aggregate carrying amount, as of the balance sheet date, of noncurrent assets not separately disclosed in the balance sheet. Noncurrent assets are expected to be realized or consumed after one year (or the normal operating cycle, if longer).

+ References

+ Details

Name:	us-gaap_OtherAssetsNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

+ Details

Name:	us-gaap_UnamortizedDebtIssuanceExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Details

Name:	us-gaap_NewAccountingPronouncementEarlyAdoptionAxis=us-gaap_NewAccountingPronouncementEarlyAdoptionEffectMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementScenarioAxis=us-gaap_ScenarioPreviouslyReportedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	wlt_EarlyAdoptionLineItemEffectAxis=wlt_DebtissuancecostlongtermdebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	wlt_EarlyAdoptionLineItemEffectAxis=wlt_DebtissuancecostothercurrentassetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	wlt_EarlyAdoptionLineItemEffectAxis=wlt_DebtissuancecostotherlongtermassetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: