Non-Qualified Retirement, Savings and Investment Plans (Details) (USD $)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Dec. 31, 2009	Dec. 31, 2013
Non-Qualified Retirement, Savings and Investment Plans [Line Items]
Number of non-qualified retirement savings and investment plans	2		2
Assets held in trust, current	$ 211,000		$ 211,000			$ 400,000
Investments held in trust	16,845,000		16,845,000			15,950,000
Executive Deferred Compensation Plan [Member]
Non-Qualified Retirement, Savings and Investment Plans [Line Items]
Investment yield, basis spread on variable rate					3.00%
Deferred compensation liability, current and long-term	9,800,000		9,800,000			11,300,000
Compensation expense	48,000	300,000	400,000	700,000
Diversified investments held in trust	4,400,000		4,400,000			4,100,000
Assets held in trust, current	200,000		200,000
Investment gains (losses)	98,000	(165,000)	(41,000)	(252,000)
Common stock held by plan	200,000		200,000			200,000
Non-Qualified Plan [Member]
Non-Qualified Retirement, Savings and Investment Plans [Line Items]
Deferred compensation liability, current and long-term	13,900,000		13,900,000			13,700,000
Investment gains (losses)	300,000	(500,000)	(100,000)	(1,100,000)
Common stock held by plan	1,300,000		1,300,000			1,400,000
Increase (decrease) in compensation expense	(100,000)	600,000	100,000	1,300,000
Investments held in trust	$ 12,600,000		$ 12,600,000			$ 12,300,000