Prepayments to equipment and construction suppliers (Schedule of Summarized the Balance of Prepayments) (Details) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Storage system project in year 2017 [Member]
Long-term Purchase Commitment [Line Items]
Balance as of December 31, 2018	$ 36.8
Prepaid / (Utilized) in 2019
Effect of foreign currency exchange rate changes	0.7
Balance as of March 31, 2019	37.5
HLJ project in year 2017 [Member]
Long-term Purchase Commitment [Line Items]
Balance as of December 31, 2018	134.2
Prepaid / (Utilized) in 2019
Effect of foreign currency exchange rate changes	2.6
Balance as of March 31, 2019	136.8
HLJ project in year 2018 [Member]
Long-term Purchase Commitment [Line Items]
Balance as of December 31, 2018	43.8
Prepaid / (Utilized) in 2019
Effect of foreign currency exchange rate changes	0.8
Balance as of March 31, 2019	44.6
HLJ project in year 2018 [Member]
Long-term Purchase Commitment [Line Items]
Balance as of December 31, 2018	35.1
Prepaid / (Utilized) in 2019
Effect of foreign currency exchange rate changes	0.7
Balance as of March 31, 2019	35.8
Nanchong project in year 2017 [Member]
Long-term Purchase Commitment [Line Items]
Balance as of December 31, 2018	3.0
Prepaid / (Utilized) in 2019
Effect of foreign currency exchange rate changes	0.1
Balance as of March 31, 2019	3.1
Nanchong project in year 2018 [Member]
Long-term Purchase Commitment [Line Items]
Balance as of December 31, 2018	249.2
Prepaid / (Utilized) in 2019
Effect of foreign currency exchange rate changes	4.8
Balance as of March 31, 2019	254.0
Total Projects [Member]
Long-term Purchase Commitment [Line Items]
Balance as of December 31, 2018	502.1
Prepaid / (Utilized) in 2019
Effect of foreign currency exchange rate changes	9.7
Balance as of March 31, 2019	$ 511.8