Fair Value of Assets and Liabilities (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013	Dec. 31, 2012
Assets:
Cash and cash equivalents	$ 52,680,000	$ 52,125,000	$ 53,161,000	$ 31,755,000
Restricted cash	24,764,000	14,592,000
Liabilities:
Borrowings under senior credit facility	337,731,000	639,246,000
5.875% Senior Notes, Due 2022
Liabilities:
Debt Instrument, Fair Value Disclosure	250,625,000	265,938,000
5.875% Senior Notes, Due 2024
Liabilities:
Debt Instrument, Fair Value Disclosure	253,750,000
6.625% Senior Notes, Due 2021
Liabilities:
Debt Instrument, Fair Value Disclosure	314,814,000	317,064,000
5.125% Senior Notes, Due 2023
Liabilities:
Debt Instrument, Fair Value Disclosure	290,439,000	279,000,000
Other non recourse debt including current portion
Liabilities:
Non-recourse debt	62,721,000	62,319,000
Carrying Value
Assets:
Cash and cash equivalents	52,680,000	52,125,000
Restricted cash	24,764,000	14,592,000
Liabilities:
Borrowings under senior credit facility	336,250,000	638,500,000
Carrying Value | 5.875% Senior Notes, Due 2022
Liabilities:
Senior Notes	250,000,000	250,000,000
Carrying Value | 5.875% Senior Notes, Due 2024
Liabilities:
Senior Notes	250,000,000
Carrying Value | 6.625% Senior Notes, Due 2021
Liabilities:
Senior Notes	300,000,000	300,000,000
Carrying Value | 5.125% Senior Notes, Due 2023
Liabilities:
Senior Notes	300,000,000	300,000,000
Carrying Value | Other non recourse debt including current portion
Liabilities:
Non-recourse debt	60,442,000	60,235,000
Level 1
Assets:
Cash and cash equivalents	52,680,000	52,125,000
Restricted cash	6,162,000	1,838,000
Liabilities:
Borrowings under senior credit facility	0	0
Level 1 | 5.875% Senior Notes, Due 2022
Liabilities:
Debt Instrument, Fair Value Disclosure	0	0
Level 1 | 6.625% Senior Notes, Due 2021
Liabilities:
Debt Instrument, Fair Value Disclosure	0	0
Level 1 | 5.125% Senior Notes, Due 2023
Liabilities:
Debt Instrument, Fair Value Disclosure	0	0
Level 1 | Other non recourse debt including current portion
Liabilities:
Non-recourse debt	0	0
Level 2
Assets:
Cash and cash equivalents	0	0
Restricted cash	18,602,000	12,754,000
Liabilities:
Borrowings under senior credit facility	337,731,000	639,246,000
Level 2 | 5.875% Senior Notes, Due 2022
Liabilities:
Debt Instrument, Fair Value Disclosure	250,625,000	265,938,000
Level 2 | 5.875% Senior Notes, Due 2024
Liabilities:
Debt Instrument, Fair Value Disclosure	253,750,000
Level 2 | 6.625% Senior Notes, Due 2021
Liabilities:
Debt Instrument, Fair Value Disclosure	314,814,000	317,064,000
Level 2 | 5.125% Senior Notes, Due 2023
Liabilities:
Debt Instrument, Fair Value Disclosure	290,439,000	279,000,000
Level 2 | Other non recourse debt including current portion
Liabilities:
Non-recourse debt	62,721,000	62,319,000
Level 3
Assets:
Cash and cash equivalents	0	0
Restricted cash	0	0
Liabilities:
Borrowings under senior credit facility	0	0
Level 3 | 5.875% Senior Notes, Due 2022
Liabilities:
Debt Instrument, Fair Value Disclosure	0	0
Level 3 | 6.625% Senior Notes, Due 2021
Liabilities:
Debt Instrument, Fair Value Disclosure	0	0
Level 3 | 5.125% Senior Notes, Due 2023
Liabilities:
Debt Instrument, Fair Value Disclosure	0	0
Level 3 | Other non recourse debt including current portion
Liabilities:
Non-recourse debt	0	0
Australian subsidiary
Liabilities:
Non-recourse debt	93,517,000	24,439,000
Australian subsidiary | Carrying Value
Liabilities:
Non-recourse debt	93,271,000	23,896,000
Australian subsidiary | Level 1
Liabilities:
Non-recourse debt	0	0
Australian subsidiary | Level 2
Liabilities:
Non-recourse debt	93,517,000	24,439,000
Australian subsidiary | Level 3
Liabilities:
Non-recourse debt	$ 0	$ 0