Energy Purchase Contracts (Tables)

12 Months Ended

Dec. 31, 2015

Energy Purchase Contracts [Line Items]

Schedule of Utility Total Expenses

	2015		2014		2013
Utility power resources	$	511,937	$	556,915	$	524,810

Future Contractual Commitments for Power Resources and Natural Gas Resources

	2016		2017		2018		2019		2020		Thereafter		Total
Power resources	$	261,560	$	168,831	$	149,375	$	145,074	$	104,688	$	838,536	$	1,668,064
Natural gas resources	79,335		64,400		65,144		57,105		45,446		427,435		738,865
Total	$	340,895	$	233,231	$	214,519	$	202,179	$	150,134	$	1,265,971	$	2,406,929

Contractual Obligations [Member]

Energy Purchase Contracts [Line Items]

Future Contractual Commitments for Power Resources and Natural Gas Resources

	2016		2017		2018		2019		2020		Thereafter		Total
Contractual obligations	$	33,694	$	31,134	$	26,405	$	31,117	$	31,811	$	192,295	$	346,456