Nature of Operations and Summary of Significant Accounting Policies Nature of Operations and Summary of Significant Accounting Policies - Effect of Adoption of Accounting Pronouncement (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Mar. 31, 2017
New Accounting Pronouncement, Early Adoption [Line Items]
Net cash used in financing activities	$ (42,558)	$ (34,427)	$ (165,033)
Net cash provided by operating activities	390,756	550,139	$ 467,315
Inventory	649,448	592,017
Accounts payable	$ 338,188	274,815
Retained earnings | New Accounting Pronouncement, Early Adoption, Effect [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Cumulative adjustment relating to the adoption of ASC 2016-16				$ 34,000
Restatement Adjustment [Member]
New Accounting Pronouncement, Early Adoption [Line Items]
Net cash used in financing activities		$ (3,300)