Income Taxes (Schedule of Components of Deferred Tax Assets and Liabilities) (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred tax assets:
Allowance for doubtful accounts	$ 1,885	$ 2,686
Tax credits	7,179	9,363
Other accruals	97,247	153,955
Net operating losses	346	304
Other	14,784	19,870
Total deferred tax assets	121,441	186,178
Deferred tax liabilities:
Inventories	55,965	76,694
Property and equipment	122,354	157,228
Other	28,528	42,422
Total deferred tax liabilities	206,847	276,344
Net deferred tax liabilities	$ (85,406)	$ (90,166)