Fair Value Measurements (Summary Of Assets And Liabilities Measured At Fair Value On A Recurring Basis) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Repossessed Assets	$ 17,700	$ 13,400
Fair Value, Measurements, Nonrecurring [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Repossessed Assets	17,700	13,400
Fair Value, Measurements, Recurring [Member] | Estimate of Fair Value Measurement [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	555,910	737,024
Marketable securities	81,448	91,140
Derivatives	16,235	32,244
Assets, Fair Value Disclosure	653,593	860,408
Derivatives, Liabilities	1,300	2,027
Fair Value, Measurements, Recurring [Member] | Quoted Prices In Active Markets For Identical Assets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	390,706	482,686
Marketable securities	36,256	33,815
Derivatives	0	0
Assets, Fair Value Disclosure	426,962	516,501
Derivatives, Liabilities	0	0
Fair Value, Measurements, Recurring [Member] | Significant Other Observable Inputs (Level 2) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	165,204	254,338
Marketable securities	45,192	57,325
Derivatives	16,235	32,244
Assets, Fair Value Disclosure	226,631	343,907
Derivatives, Liabilities	1,300	2,027
Fair Value, Measurements, Recurring [Member] | Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Marketable securities	0	0
Derivatives	0	0
Assets, Fair Value Disclosure	0	0
Derivatives, Liabilities	0	0
Fair value, adjustment [Domain]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Repossessed Assets	$ 8,600	$ 5,000