Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Mar. 31, 2017	Dec. 31, 2016
Fair Value, Measurements, Recurring [Member]
Financial Assets:
Cash and cash equivalents	$ 102,932	$ 72,031
Restricted cash	17,423	17,943
Total Financial Assets	120,355	89,974
Financial Liabilities:
Total debt	1,605,794	1,622,811
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Financial Assets:
Cash and cash equivalents	102,932	72,031
Restricted cash	0	0
Total Financial Assets	102,932	72,031
Financial Liabilities:
Total debt	0	0
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Financial Assets:
Cash and cash equivalents	0	0
Restricted cash	17,423	17,943
Total Financial Assets	17,423	17,943
Financial Liabilities:
Total debt	1,605,794	1,622,811
Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Financial Assets:
Cash and cash equivalents	0	0
Restricted cash	0	0
Total Financial Assets	0	0
Financial Liabilities:
Total debt	0	0
Interest Rate Swap [Member]
Derivative Instruments and Hedging Disclosure:
Asset for interest rate swap agreements	6,479	5,400
Liability for interest rate swap agreements	893	2,300
Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member]
Derivative Instruments and Hedging Disclosure:
Asset for interest rate swap agreements	6,479	5,392
Liability for interest rate swap agreements	893	2,283
Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 1 [Member]
Derivative Instruments and Hedging Disclosure:
Asset for interest rate swap agreements	0	0
Liability for interest rate swap agreements	0	0
Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 2 [Member]
Derivative Instruments and Hedging Disclosure:
Asset for interest rate swap agreements		5,392
Liability for interest rate swap agreements		2,283
Interest Rate Swap [Member] | Fair Value, Measurements, Recurring [Member] | Fair Value, Inputs, Level 3 [Member]
Derivative Instruments and Hedging Disclosure:
Asset for interest rate swap agreements	0	0
Liability for interest rate swap agreements	$ 0	$ 0