Summary of Significant Accounting Policies Regulatory Liabilities Disclosure (details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013		Dec. 31, 2012
Regulatory Liabilities [Line Items]
Current Regulatory Liabilities	$ 28,335		$ 20,792
Regulatory liabilities	303,485		288,113
Gas Costs Payable [Member]
Regulatory Liabilities [Line Items]
Current Regulatory Liabilities	7,510		9,100
Regulatory liabilities	2,172		0
Unrealized Gain On Derivatives [Member]
Regulatory Liabilities [Line Items]
Current Regulatory Liabilities	5,290	[1]	1,950	[1]
Regulatory liabilities	1,880	[1]	3,639	[1]
Other Regulatory [Member]
Regulatory Liabilities [Line Items]
Current Regulatory Liabilities	15,535	[2]	9,742	[2]
Regulatory liabilities	3,139	[2]	3,261	[2]
Accrued Asset Removal Costs [Member]
Regulatory Liabilities [Line Items]
Regulatory liabilities	$ 296,294		$ 281,213

[1] Unrealized gains or losses on derivatives are non-cash items and, therefore, do not earn a rate of return or a carrying charge. These amounts are recoverable through utility rates as part of the annual PGA mechanism when realized at settlement.

[2] Other primarily consists of several deferrals and amortizations under other approved regulatory mechanisms. The accounts being amortized typically earn a rate of return or carrying charge.