Commitments, Guarantees and Contingencies - North Dakota Wind Development (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012 DC Transmission Line from Square Butte [Member] kV Miles	Dec. 31, 2013 Bison Wind Energy Center [Member] MW	Dec. 31, 2013 Bison 4 Wind Project [Member] MW
North Dakota Wind Development [Line Items]
Transmission Line Length (Miles)	465
Transmission Line Capacity (kV)	250
Generating Unit Capacity (MW)		292	205
Estimated Capital Expenditures			$ 345
Capital Cost Spent to Date			55.6
Minimum Payment Obligation in 2014			$ 244.4

Minimum amount of other commitment maturing in the next fiscal year following the latest fiscal year for commitments not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in this taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

No definition available.

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