Summary of Significant Accounting Policies (Recently Adopted and Issued Accounting Pronoucements) (Details 1) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net Cash Provided by Operating Activities	$ 261,256	$ 70,651	$ 313,499
Cash and Cash Equivalents and Restricted Cash at Beginning of Year	774,952		653,488
Net (Decrease) Increase in Cash and Cash Equivalents and Restricted Cash	(104,136)	(23,932)	145,396
Cash and Cash Equivalents and Restricted Cash at End of Year	670,816	774,952
Previous Accounting Guidance [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in Restricted Cash		4,153	58,871
Net Cash Provided by Operating Activities		74,804	372,370
Cash and Cash Equivalents and Restricted Cash at Beginning of Year	754,207	773,986	569,719
Net (Decrease) Increase in Cash and Cash Equivalents and Restricted Cash		(19,779)	204,267
Cash and Cash Equivalents and Restricted Cash at End of Year		754,207	773,986
Adjustments for New Accounting Pronouncement [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in Restricted Cash		(4,153)	(58,871)
Net Cash Provided by Operating Activities		(4,153)	(58,871)
Cash and Cash Equivalents and Restricted Cash at Beginning of Year	20,745	24,898	83,769
Net (Decrease) Increase in Cash and Cash Equivalents and Restricted Cash		(4,153)	(58,871)
Cash and Cash Equivalents and Restricted Cash at End of Year		20,745	24,898
New Accounting Pronouncement, Early Adoption, Effect [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in Restricted Cash		0	0
Net Cash Provided by Operating Activities		70,651	313,499
Cash and Cash Equivalents and Restricted Cash at Beginning of Year	$ 774,952	798,884	653,488
Net (Decrease) Increase in Cash and Cash Equivalents and Restricted Cash		(23,932)	145,396
Cash and Cash Equivalents and Restricted Cash at End of Year		$ 774,952	$ 798,884