Fair Value Measurements (Details) - Recurring - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016
Quoted Prices in Active Markets for Identical Assets (Level 1)
Assets:
Cash and cash equivalents	$ 481,035	$ 455,579
Restricted cash and cash equivalents	49,613	53,238
Derivative Asset	0	0
Total	530,648	508,817
Significant Other Observable Inputs (Level 2)
Assets:
Cash and cash equivalents	0	0
Restricted cash and cash equivalents	0	0
Derivative Asset	3,023	5,735
Total	3,023	5,735
Significant Unobservable Inputs (Level 3)
Assets:
Cash and cash equivalents	0	0
Restricted cash and cash equivalents	0	0
Derivative Asset	0	0
Total	0	0
Estimate of Fair Value Measurement [Member]
Assets:
Cash and cash equivalents	481,035	455,579
Restricted cash and cash equivalents	49,613	53,238
Derivative Asset	3,023	5,735
Total	$ 533,671	$ 514,552