Interest Expense (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Nov. 20, 2012
Debt Instrument [Line Items]
Interest incurred on debt	$ 21,373	$ 21,589	$ 10,172
Amortization of discount on Senior Subordinated Notes	12,298	11,493	10,742
Amortization of debt issuance costs	3,339	2,504	1,712
Supply Chain Financing mark-up	47	451	621
Total interest expense	$ 37,057	$ 36,037	$ 23,247
Effective interest rate, revolving credit facility	2.17%	2.42%
Senior subordinated notes implied rate	7.00%
Senior Notes [Member]
Debt Instrument [Line Items]
Stated interest rate				6.375%