Other Comprehensive Income (Loss) (Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Dec. 31, 2015
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in other comprehensive loss, net of tax	$ 809,106	$ 2,701,589	$ 6,261,538	$ 5,967,976
Net unrealized gains
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in other comprehensive loss, net of tax	1,040	895
Foreign currency translation loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in other comprehensive loss, net of tax	(328,855)	(354,329)
Accumulated other comprehensive loss
Accumulated Other Comprehensive Income (Loss) [Line Items]
Change in other comprehensive loss, net of tax	$ (327,815)	$ (353,434)