Energy Purchase Contracts (Tables)

12 Months Ended

Dec. 31, 2014

Energy Purchase Contracts [Line Items]

Schedule of Utility Total Expenses

	2014		2013		2012
Utility power resources	$	556,915	$	524,810	$	523,416

Future Contractual Commitments for Power Resources and Natural Gas Resources

	2015		2016		2017		2018		2019		Thereafter		Total
Power resources	$	277,474	$	209,255	$	144,424	$	132,897	$	125,332	$	860,731	$	1,750,113
Natural gas resources	82,884		56,504		57,379		52,936		49,304		455,975		754,982
Total	$	360,358	$	265,759	$	201,803	$	185,833	$	174,636	$	1,316,706	$	2,505,095

Contractual Obligations [Member]

Energy Purchase Contracts [Line Items]

Future Contractual Commitments for Power Resources and Natural Gas Resources

	2015		2016		2017		2018		2019		Thereafter		Total
Contractual obligations	$	29,133	$	35,692	$	28,189	$	25,659	$	28,969	$	193,734	$	341,376