Income taxes: (Tables)

12 Months Ended

Dec. 31, 2013

Income taxes:

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

	2013		2012		2011
Statutory federal income tax rate	35.0	%	35.0	%	35.0%
Patronage exclusion	(33.3	%)	(32.7	%)	(32.6%)
Tax credits	0.0	%	0.0	%	0.0%
Other	(1.7	%)	(2.3	%)	(2.4%)
Effective income tax rate	0.0	%	0.0	%	0.0%

Schedule of components of net deferred tax assets and liabilities

		(dollars in thousands)
		2013			2012
Deferred tax assets
Net operating losses	$	29,724		$	29,724
Tax credits (alternative minimum tax and other)		1,478			1,535
Accounting for Rocky Mountain transactions		348,136			347,867
Other assets		23,233			18,859
Deferred tax assets		402,571			397,985
Less: Valuation allowance		(31,202	)		(31,259	)
Net deferred tax assets	$	371,369		$	366,726
Deferred tax liabilities
Depreciation	$	448,350		$	465,598
Accounting for Rocky Mountain transactions		153,173			157,145
Other liabilities		60,354			44,508
Deferred tax liabilities		661,877			667,251
Net deferred tax liabilities		290,508			300,525
Less: Patronage exclusion		(290,508	)		(300,525	)
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		1,478		–
	$	1,478	$	76,411