Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Netting and Collateral
Fair value measurement, additional disclosure
Total Assets	$ (1,000)
Total liabilities	(800)
Fair value measured on recurring basis \| Level 1
Assets:
Total assets	14,038	785
Liabilities:
Total liabilities	10,148	2,226
Fair value measured on recurring basis \| Level 1 \| Cash equivalents
Assets:
Total assets		32
Fair value measured on recurring basis \| Level 1 \| Commodity contracts
Assets:
Total assets	14,038	753
Liabilities:
Total liabilities	10,148	2,226
Fair value measured on recurring basis \| Level 2
Assets:
Total assets	57,449	17,915
Liabilities:
Total liabilities	47,796	15,861
Fair value measured on recurring basis \| Level 2 \| Commodity contracts
Assets:
Total assets	51,033	14,139
Liabilities:
Total liabilities	46,754	14,926
Fair value measured on recurring basis \| Level 2 \| Foreign currency contracts
Assets:
Total assets	2,994	461
Liabilities:
Total liabilities	1,018	574
Fair value measured on recurring basis \| Level 2 \| Hedged item inventories
Assets:
Total assets	3,216	2,518
Fair value measured on recurring basis \| Level 2 \| Hedged item commitments
Assets:
Total assets	206	797
Liabilities:
Total liabilities	24	361
Fair value measured on recurring basis \| Level 3
Assets:
Total assets		123
Liabilities:
Total liabilities	4,194	5,045
Fair value measured on recurring basis \| Level 3 \| Commodity contracts
Assets:
Total assets		123
Liabilities:
Total liabilities		33
Fair value measured on recurring basis \| Level 3 \| Earn-out
Liabilities:
Total liabilities	4,194	5,012
Fair value measured on recurring basis \| Sub-Total
Assets:
Total assets	71,487	18,823
Liabilities:
Total liabilities	62,138	23,132
Fair value measured on recurring basis \| Sub-Total \| Cash equivalents
Assets:
Total assets		32
Fair value measured on recurring basis \| Sub-Total \| Commodity contracts
Assets:
Total assets	65,071	15,015
Liabilities:
Total liabilities	56,902	17,185
Fair value measured on recurring basis \| Sub-Total \| Foreign currency contracts
Assets:
Total assets	2,994	461
Liabilities:
Total liabilities	1,018	574
Fair value measured on recurring basis \| Sub-Total \| Hedged item inventories
Assets:
Total assets	3,216	2,518
Fair value measured on recurring basis \| Sub-Total \| Hedged item commitments
Assets:
Total assets	206	797
Liabilities:
Total liabilities	24	361
Fair value measured on recurring basis \| Sub-Total \| Earn-out
Liabilities:
Total liabilities	4,194	5,012
Fair value measured on recurring basis \| Netting and Collateral
Fair value measurement, additional disclosure
Total Assets	(44,168)	(7,542)
Total liabilities	(44,184)	(8,933)
Fair value measured on recurring basis \| Netting and Collateral \| Commodity contracts
Fair value measurement, additional disclosure
Total Assets	(43,275)	(7,000)
Total liabilities	(43,291)	(8,391)
Fair value measured on recurring basis \| Netting and Collateral \| Foreign currency contracts
Fair value measurement, additional disclosure
Total Assets	(893)	(277)
Total liabilities	(893)	(277)
Fair value measured on recurring basis \| Netting and Collateral \| Hedged item commitments
Fair value measurement, additional disclosure
Total Assets		(265)
Total liabilities		(265)
Fair value measured on recurring basis \| Total
Assets:
Total assets	27,319	11,281
Liabilities:
Total liabilities	17,954	14,199
Fair value measured on recurring basis \| Total \| Cash equivalents
Assets:
Total assets		32
Fair value measured on recurring basis \| Total \| Commodity contracts
Assets:
Total assets	21,796	8,015
Liabilities:
Total liabilities	13,611	8,794
Fair value measured on recurring basis \| Total \| Foreign currency contracts
Assets:
Total assets	2,101	184
Liabilities:
Total liabilities	125	297
Fair value measured on recurring basis \| Total \| Hedged item inventories
Assets:
Total assets	3,216	2,518
Fair value measured on recurring basis \| Total \| Hedged item commitments
Assets:
Total assets	206	532
Liabilities:
Total liabilities	24	96
Fair value measured on recurring basis \| Total \| Earn-out
Liabilities:
Total liabilities	$ 4,194	$ 5,012