Stockholder's Equity (Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Accumulated Other Comprehensive Income (Loss)
Balances at beginning of period	$ 14,925,452	$ 15,281,472	$ 15,175,885
OCI, net of tax	(41,288)	80,414	(78,833)
Balances at end of period	15,586,599	14,925,452	15,281,472
Foreign Currency Translation
Accumulated Other Comprehensive Income (Loss)
Balances at beginning of period	(110,581)	(173,496)
OCI, before reclassifications, net of tax	(18,648)	62,915
Reclassification		0
OCI, net of tax		62,915
Balances at end of period	(129,229)	(110,581)	(173,496)
Available for Sale Securities
Accumulated Other Comprehensive Income (Loss)
Balances at beginning of period	0	5,120
OCI, before reclassifications, net of tax	0	0
Reclassification		(5,120)
OCI, net of tax		(5,120)
Balances at end of period	0	0	5,120
Actuarial losses
Accumulated Other Comprehensive Income (Loss)
Balances at beginning of period	(884)	(1,153)
OCI, before reclassifications, net of tax	344	269
Reclassification		0
OCI, net of tax		269
Balances at end of period	(540)	(884)	(1,153)
Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss)
Balances at beginning of period	0	(2)
OCI, before reclassifications, net of tax	0	2
Reclassification		0
OCI, net of tax		2
Balances at end of period	0	0	(2)
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss)
Balances at beginning of period	(111,465)	(169,531)	(88,243)
OCI, before reclassifications, net of tax	(18,304)	63,186
Reclassification		(5,120)
OCI, net of tax	(18,304)	58,066	(81,288)
Balances at end of period	$ (129,769)	$ (111,465)	$ (169,531)