Summary of Significant Accounting Policies (Adjustment of Previously Reported Financial Information, Narrative) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended			168 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2016
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase to other income									$ (128,226)	$ (111,998)	$ (134,287)
Decrease to Income taxes									(1,971)	(2,673)	(2,590)
(Increase) decrease to net income	$ 200,291	$ 55,734	$ 51,057	$ 59,063	$ 83,841	$ 93,695	$ 36,526	$ 31,862	366,145	245,924	224,471
Restatement of Net Profit (Loss) [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase to other income										(111,998)	(134,287)
Decrease to Income taxes										(2,673)	(2,590)
(Increase) decrease to net income										245,924	224,471
Adjustment [Member] | Restatement of Net Profit (Loss) [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Increase to other income										918	(69)	$ 12,700
Decrease to Income taxes										560	377	$ 3,900
(Increase) decrease to net income									$ (500)	$ 1,478	$ 308