Fair Value Measurements (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Assets:
Total	$ 5,341	$ 32,587
Liabilities:
Interest rate derivative financial instruments	39,724	28,653
Total	39,724	28,653
Level 1 [Member]
Assets:
Total	0	0
Liabilities:
Interest rate derivative financial instruments	0	0
Total	0	0
Level 2 [Member]
Assets:
Total	5,341	32,587
Liabilities:
Interest rate derivative financial instruments	39,724	28,653
Total	39,724	28,653
Investments [Member]
Assets:
Investments, Fair Value Disclosure	5,253	12,283
Investments [Member] | Level 1 [Member]
Assets:
Investments, Fair Value Disclosure		0
Investments [Member] | Level 2 [Member]
Assets:
Investments, Fair Value Disclosure	5,253	12,283
Demand Obligation [Member]
Assets:
Investments, Fair Value Disclosure	88	20,304
Demand Obligation [Member] | Level 1 [Member]
Assets:
Investments, Fair Value Disclosure	0	0
Demand Obligation [Member] | Level 2 [Member]
Assets:
Investments, Fair Value Disclosure	$ 88	$ 20,304