Description of Business and Basis of Presentation (Recently Issued Accounting Standards) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase (decrease) in net cash provided by operating activities	$ 211,649	$ 117,702	$ 154,302
Increase (decrease) in net cash provided by investing activities	112,110	465,849	35,103
Accounting Standards Update 2016-15 | New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase (decrease) in net cash provided by operating activities		6,400
Increase (decrease) in net cash provided by investing activities			(2,900)
Accounting Standards Update 2016-18 | New Accounting Pronouncement, Early Adoption, Effect
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Increase (decrease) in net cash provided by operating activities			(263)
Increase (decrease) in net cash provided by investing activities		$ 11,300	$ (475)
Accounting Standards Update 2017-05 | Distributions in Excess of Cumulative Net Income
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Cumulative effect from change in accounting principle	$ 24,300