Income Taxes (Effective Income Tax Reconciliation) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal	$ 6,363	$ (2,524)	$ (26,160)
Federal income tax rate (percent)	35.00%	35.00%	35.00%
State, net of federal benefit	$ 53	$ (202)	$ (543)
State income tax rate, net of federal benefit (percent)	0.30%	2.80%	0.70%
Foreign differential	$ (11,768)	$ (12,624)	$ (3,678)
Foreign differential (percent)	(64.70%)	175.00%	4.90%
Enacted changes in tax law	$ 17,645	$ 0	$ 0
Enacted changes in tax law (percent)	97.10%	0.00%	0.00%
Non-deductible / non-taxable items	$ 6,006	$ 2,694	$ (2,181)
Non-deductible / non-taxable items (percent)	33.00%	(37.40%)	2.90%
Change in valuation allowance	$ 24,400	$ 16,041	$ 10,892
Change in valuation allowance (percent)	134.20%	(222.40%)	(14.50%)
U.S. tax on foreign earnings	$ (32,427)	$ 23,130	$ 82,311
U.S. tax on foreign earnings (percent)	(178.40%)	(320.60%)	(110.00%)
Foreign tax credits	$ (7,980)	$ (18,581)	$ (49,432)
Foreign tax credits (percent)	(43.90%)	257.60%	66.10%
Uncertain tax positions	$ 1,054	$ 19	$ (3,952)
Uncertain tax positions (percent)	5.80%	(0.30%)	5.30%
Audit settlements	$ 354	$ 253	$ 1,167
Audit settlements (percent)	1.90%	(3.50%)	(1.60%)
Stock compensation windfall / shortfall	$ 882	$ 2,120	$ 0
Stock compensation windfall / shortfall (percent)	4.90%	(29.40%)	(0.00%)
Deferred income tax account adjustments	$ 2,679	$ (842)	$ 0
Deferred income tax account adjustments (percent)	14.70%	11.70%	0.00%
Other	$ 681	$ (203)	$ 28
Other (percent)	3.80%	2.80%	(0.10%)
Income tax expense	$ 7,942	$ 9,281	$ 8,452
Effective tax rate (percent)	43.70%	(128.70%)	(11.30%)