Income Tax (Provision for Income Tax Expense Computed from Statutory Rate to Pre-tax Income) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effective Income Tax Rate Reconciliation, Amount [Abstract]
Effective Income Tax Rate Reconciliation at Federal Statutory Income Tax Rate, Amount	$ 352,987	$ 222,339	$ 321,728
Effective Income Tax Rate Reconciliation, Foreign Income Tax Rate Differential, Amount	(12,483)	(8,032)	(14,705)
Income Tax Reconciliation Foreign Income Tax Basis Differential	(8,256)	(26,484)	(21,086)
Effective Income Tax Rate Reconciliation, Change in Deferred Tax Assets Valuation Allowance, Amount	2,076	26,507	635
Effective Income Tax Rate Reconciliation, Tax Contingency, Domestic, Amount	(9,083)	9,034	2,260
Income Tax Reconciliation Change In Canadian Enacted Tax Rate	0	(414)	1,374
Income Tax Reconciliation Change In Foreign Enacted Tax Rate	280	(1,184)	(1,070)
Income Tax Reconciliation Subpart F	6,132	8,255	13,571
Effective Income Tax Rate Reconciliation, Tax Credit, Foreign, Amount	(1,045)	(1,786)	(7,808)
Effective Income Tax Rate Reconciliation, Prior Year Income Taxes, Amount	(8,123)	(12,465)	(7,351)
Effective Income Tax Rate Reconciliation, Other Adjustments, Amount	2,001	647	(218)
Income Tax Expense (Benefit)	$ 324,486	$ 216,417	$ 287,330
Effective Income Tax Rate Reconciliation, Percent	32.20%	34.10%	31.30%