Income taxes: (Tables)

12 Months Ended

Dec. 31, 2012

Income taxes:

Summary of difference between statutory federal income tax rate on income before income taxes and effective income tax rate

	2012		2011		2010
Statutory federal income tax rate	35.0	%	35.0	%	35.0%
Patronage exclusion	(32.7	%)	(32.6	%)	(32.9%)
Tax credits	0.0	%	0.0	%	0.0%
Other	(2.3	%)	(2.4	%)	(2.1%)
Effective income tax rate	0.0	%	0.0	%	0.0%

Schedule of components of net deferred tax assets and liabilities

		(dollars in thousands)
		2012			2011
Deferred tax assets
Net operating losses	$	29,724		$	29,724
Tax credits (alternative minimum tax and other)		1,535			1,535
Accounting for Rocky Mountain transactions		347,867			334,423
Other assets		18,859			14,312
Deferred tax assets		397,985			379,994
Less: Valuation allowance		(31,259	)		(31,259	)
Net deferred tax assets	$	366,726		$	348,735
Deferred tax liabilities
Depreciation	$	465,598		$	485,721
Accounting for Rocky Mountain transactions		157,145			161,214
Other liabilities		44,508			39,109
Deferred tax liabilities		667,251			686,044
Net deferred tax liabilities		300,525			337,309
Less: Patronage exclusion		(300,525	)		(337,309	)
Net deferred taxes	$	–		$	–

Schedule of federal tax net operating loss carryforwards and alternative minimum tax credits

		(dollars in thousands)
Expiration Date		Minimum Alternative Tax Credits		NOLs
2018	$	–	$	61,533
2019		–		10,516
2020		–		4,362
None		1,535		–
	$	1,535	$	76,411