Fair Value Measurements (Details)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Number of domestic regions	2
Fair Value, Inputs, Level 2 [Member]
Assets:
Interest Rate Derivative Assets, at Fair Value	$ 9,484,000	$ 31,000
Total	12,750,000	4,397,000
Liabilities:
Interest rate derivative financial instruments	24,411,000	31,153,000
Total	24,411,000	31,153,000
Investments [Member] | Fair Value, Inputs, Level 2 [Member]
Assets:
Investments, Fair Value Disclosure	3,254,000	4,235,000
Demand Obligation [Member] | Fair Value, Inputs, Level 2 [Member]
Assets:
Investments, Fair Value Disclosure	$ 12,000	$ 131,000