Gas Reserves (details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Gas Reserves [Abstract]
Gas Reserves Percent Gas Supplies YTD	3.00%
Gas Reserves, Current	$ 14,286	$ 14,966	$ 6,732
Gas Reserves Noncurrent Gross	110,033	92,179	63,546
Gas Reserves Amortization	9,864	7,486	2,440
Total Gas Reserves	114,455	99,659	67,838
Deferred Taxes Related To Gas Reserves	32,907	28,329	22,047
Net Gas Reserves Investment	$ 81,548	$ 71,330	$ 45,791