XML 67 R42.htm IDEA: XBRL DOCUMENT v3.7.0.1
Future Lease Payment Under Terms of Capacity Purchase Agreement (Detail)
$ in Billions
Jun. 30, 2017
USD ($)
Long-term Purchase Commitment [Line Items]  
Last six months of 2017 $ 0.9
2018 2.0
2019 1.5
2020 1.2
2021 1.1
After 2021 4.2
Contractual Obligation, Total $ 10.9