Annual report pursuant to Section 13 and 15(d)

Hurricane Remediation and Insurance Claims - Additional Information (Details)

v2.4.1.9
Hurricane Remediation and Insurance Claims - Additional Information (Details) (USD $)
In Millions, unless otherwise specified
3 Months Ended 12 Months Ended
Sep. 30, 2008
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Insurance [Abstract]        
Retention amount per occurrence $ 10.0us-gaap_ReinsuranceRetentionPolicyAmountRetained      
Maximum insurance coverage policy limit due to named windstorms for per incident 150.0wti_MaximumInsuranceCoveragePolicyLimitDueToNamedWindstormsForPerIncident      
Maximum insurance coverage policy limit except for property damage due to named windstorms 250.0wti_MaximumCoveragePerIncidentExceptPropertyDamage      
Insurance proceeds   12.2us-gaap_ProceedsFromInsuranceSettlementOperatingActivities 6.7us-gaap_ProceedsFromInsuranceSettlementOperatingActivities 2.9us-gaap_ProceedsFromInsuranceSettlementOperatingActivities
Cumulative insurance recoveries related to hurricanes   $ 161.2us-gaap_InsuranceRecoveries