Income Taxes (Schedule of Effective Income Tax Rate Reconciliation) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Examination [Line Items]
Income tax expense at U.S. federal rate									$ 62,845	$ 54,519	$ 49,705
Income tax expense at U.S. federal rate, percent									35.00%	35.00%	35.00%
State income taxes, net of frderal income tax benefit									3,029	1,510	1,376
State income taxes, net of frderal income tax benefit, percent									1.70%	1.00%	1.00%
Stock option activity									254	516	440
Stock option activity, percent									0.10%	0.30%	0.30%
Non-U.S. witholding taxes, net of federal income tax effect, and foreign tax credits									310	307	346
Non-U.S. witholding taxes, net of federal income tax effect, and foreign tax credits, percent									0.20%	0.20%	0.20%
Net change in valuation allowance related to non-U.S. deffered tax assets, primarily net operating losses									(1,842)	(630)	394
Net change in valuation allowance related to non-U.S. deffered tax assets, primarily net operating losses, percent									(1.00%)	(0.40%)	0.30%
Difference between U.S. federal statutory and foreign tax rates									(2,513)	(2,777)	(2,393)
Difference between U.S. federal statutory and foreign tax rates, percent									(1.40%)	(1.80%)	(1.70%)
Change in unrecognized tax benefits									(211)	967	3,126
Changes in unrecognized tax benefits, percent									(0.10%)	0.60%	2.20%
Other tax credits									(4,374)	(1,494)	(7,734)
Other tax credits, percent									(2.50%)	(1.00%)	(5.40%)
Recognition of deferred tax assets									(1,448)	0	(1,778)
Recognition of deferred tax assets, percent									(0.80%)	0.00%	(1.30%)
Other - net									(19)	(40)	176
Other - net, percent									0.00%	0.00%	0.10%
Income tax expense	$ 13,384	$ 14,265	$ 15,955	$ 12,427	$ 11,437	$ 15,186	$ 14,744	$ 11,511	$ 56,031	$ 52,878	$ 43,658
Incomr tax expense, percent									31.20%	33.90%	30.70%