Supplemental Financial Information (Parent - Cash Flow Statement) (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015
Operating Activities [Abstract]
Net Cash Provided by (Used in) Operating Activities	$ 170,798	$ 411,205
Investing Activities [Abstract]
Net Cash Provided by (Used in) Investing Activities	(200,102)	(404,987)
Financing Activities [Abstract]
Payments of Financing Costs	0	(6)
Repurchased shares - net share settlements	319	2,507
Net Cash Provided by (Used in) Financing Activities	368,681	10,450
Cash and Cash Equivalents, Period Increase (Decrease)	339,377	16,668
Cash and Cash Equivalents, at Carrying Value	4,143	8,919
Cash and Cash Equivalents, at Carrying Value	343,520	25,587
Parent [Member]
Operating Activities [Abstract]
Net Cash Provided by (Used in) Operating Activities	(23,927)	(51,939)
Investing Activities [Abstract]
Dividends received	24,089	73,021
Net Cash Provided by (Used in) Investing Activities	24,089	73,021
Financing Activities [Abstract]
Shares reissued from treasury	(337)	4,712
Payments of Financing Costs	0	6
Repurchased shares - net share settlements	(94)	0
Net Cash Provided by (Used in) Financing Activities	(431)	4,718
Cash and Cash Equivalents, Period Increase (Decrease)	(269)	25,800
Cash and Cash Equivalents, at Carrying Value	523	772
Cash and Cash Equivalents, at Carrying Value	$ 254	$ 26,572