Recent Accounting Developments Recent Accounting Developments (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in cash flows from operating activities reclassified to investing activities	$ 86,328	$ 61,040
Increase in cash flows from investing activities reclassified from operating activities	$ (56,768)	(50,851)
Accounting Standards Update 2016-15 [Member]
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Decrease in cash flows from operating activities reclassified to investing activities		(3,600)
Increase in cash flows from investing activities reclassified from operating activities		$ 3,600