Unrecorded Unconditional Purchase Obligation (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 1,098,194
Purchase Commitment [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Less than 1 year	349,513
1 - 3 years	227,586
3 - 5 years	128,338
More than 5 years	414,276
Total Purchase Obligations	1,119,713
Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	965,884
More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	132,310
More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Standby Letters of Credit [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	329,849
Standby Letters of Credit [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	207,452
Standby Letters of Credit [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	122,397
Standby Letters of Credit [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Standby Letters of Credit [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Surety Bonds [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	768,345
Surety Bonds [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	758,432
Surety Bonds [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	9,913
Surety Bonds [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Surety Bonds [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Employee Related Commitments [Member] | Standby Letters of Credit [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	190,158
Employee Related Commitments [Member] | Standby Letters of Credit [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	126,654
Employee Related Commitments [Member] | Standby Letters of Credit [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	63,504
Employee Related Commitments [Member] | Standby Letters of Credit [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Employee Related Commitments [Member] | Standby Letters of Credit [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Employee Related Commitments [Member] | Surety Bonds [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	204,884
Employee Related Commitments [Member] | Surety Bonds [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	204,884
Employee Related Commitments [Member] | Surety Bonds [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Employee Related Commitments [Member] | Surety Bonds [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Employee Related Commitments [Member] | Surety Bonds [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Environment Related Commitments [Member] | Standby Letters of Credit [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	56,293
Environment Related Commitments [Member] | Standby Letters of Credit [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	34,346
Environment Related Commitments [Member] | Standby Letters of Credit [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	21,947
Environment Related Commitments [Member] | Standby Letters of Credit [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Environment Related Commitments [Member] | Standby Letters of Credit [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Environment Related Commitments [Member] | Surety Bonds [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	533,974
Environment Related Commitments [Member] | Surety Bonds [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	524,072
Environment Related Commitments [Member] | Surety Bonds [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	9,902
Environment Related Commitments [Member] | Surety Bonds [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Environment Related Commitments [Member] | Surety Bonds [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Other Commitments [Member] | Standby Letters of Credit [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	83,398
Other Commitments [Member] | Standby Letters of Credit [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	46,452
Other Commitments [Member] | Standby Letters of Credit [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	36,946
Other Commitments [Member] | Standby Letters of Credit [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Other Commitments [Member] | Standby Letters of Credit [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Other Commitments [Member] | Surety Bonds [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	29,487
Other Commitments [Member] | Surety Bonds [Member] | Balance on First Anniversary [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	29,476
Other Commitments [Member] | Surety Bonds [Member] | More Than One And Within Three Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	11
Other Commitments [Member] | Surety Bonds [Member] | More Than Three And Within Five Years From Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	0
Other Commitments [Member] | Surety Bonds [Member] | Beyond Five Years of Balance Sheet Date [Member]
Unrecorded Unconditional Purchase Obligation [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted	$ 0