Income Taxes (Unrecognized Tax Benefits) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits
Balance at beginning of year	$ 124,728	$ 139,249	$ 132,495
Increases from prior period positions	528	0	7,637
Decreases from prior period positions	(31,470)	(21,207)	(16,753)
Increases from current period positions	5,951	10,867	23,533
Decreases relating to settlements with tax authorities	(6,953)	(1,791)	(3,831)
Reductions from lapse of applicable statute of limitations	(3,017)	(2,390)	(3,832)
Balance at end of year	$ 89,767	$ 124,728	$ 139,249