Organization and Summary of Significant Accounting Policies (Details 10) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Assets at fair value and gains (losses) recorded
Equipment held for sale	$ 32,491,000	$ 23,607,000
Total losses on equipment held for sale	(6,461,000)	(5,874,000)
Total losses on assets	(6,461,000)	(5,874,000)
Asset write-down	6,461,000	5,874,000	3,341,000
Nonrecurring
Assets at fair value and gains (losses) recorded
Asset write-down recorded earlier	3,700,000	4,700,000
Asset write-down	2,800,000	1,200,000
Nonrecurring | Total
Assets at fair value and gains (losses) recorded
Equipment held for sale	32,491,000	23,607,000
Assets at fair value	32,491,000	23,607,000
Nonrecurring | Level 2
Assets at fair value and gains (losses) recorded
Equipment held for sale	30,824,000	23,384,000
Assets at fair value	30,824,000	23,384,000
Nonrecurring | Level 3
Assets at fair value and gains (losses) recorded
Equipment held for sale	1,667,000	223,000
Assets at fair value	$ 1,667,000	$ 223,000