Fair Value of Financial Instruments - Financial Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Dec. 31, 2013 Quoted Prices in Active Markets (Level 1) [Member] Mark-to-market energy liabilities [Member]	Dec. 31, 2013 Quoted Prices in Active Markets (Level 1) [Member] Investments in equity securities [Member]	Dec. 31, 2013 Quoted Prices in Active Markets (Level 1) [Member] Investments - other [Member]	Dec. 31, 2013 Quoted Prices in Active Markets (Level 1) [Member] Mark To Market Energy Assets Including Put Option [Member]	Dec. 31, 2013 Significant Other Observable Inputs (Level 2) [Member] Mark-to-market energy liabilities [Member]	Dec. 31, 2013 Significant Other Observable Inputs (Level 2) [Member] Investments in equity securities [Member]	Dec. 31, 2013 Significant Other Observable Inputs (Level 2) [Member] Investments - other [Member]	Dec. 31, 2013 Significant Other Observable Inputs (Level 2) [Member] Mark To Market Energy Assets Including Put Option [Member]	Dec. 31, 2013 Significant Unobservable Inputs (Level 3) [Member] Mark-to-market energy liabilities [Member]	Dec. 31, 2013 Significant Unobservable Inputs (Level 3) [Member] Investments in equity securities [Member]	Dec. 31, 2013 Significant Unobservable Inputs (Level 3) [Member] Investments - other [Member]	Dec. 31, 2013 Recurring [Member] Mark-to-market energy liabilities [Member]	Dec. 31, 2013 Recurring [Member] Investments in equity securities [Member]	Dec. 31, 2013 Recurring [Member] Investments - other [Member]	Dec. 31, 2013 Recurring [Member] Mark To Market Energy Assets Including Put Option [Member]	Jun. 30, 2013 Recurring [Member] Estimate of Fair Value, Fair Value Disclosure [Member] Investments in guaranteed income fund [Member]	Jun. 30, 2013 Recurring [Member] Estimate of Fair Value, Fair Value Disclosure [Member] Investments - other [Member]	Jun. 30, 2013 Recurring [Member] Quoted Prices in Active Markets (Level 1) [Member] Investments in guaranteed income fund [Member]	Jun. 30, 2013 Recurring [Member] Quoted Prices in Active Markets (Level 1) [Member] Investments - other [Member]	Jun. 30, 2013 Recurring [Member] Significant Other Observable Inputs (Level 2) [Member] Investments in guaranteed income fund [Member]	Jun. 30, 2013 Recurring [Member] Significant Other Observable Inputs (Level 2) [Member] Investments - other [Member]	Jun. 30, 2013 Recurring [Member] Significant Unobservable Inputs (Level 3) [Member] Investments in guaranteed income fund [Member]	Jun. 30, 2013 Recurring [Member] Significant Unobservable Inputs (Level 3) [Member] Investments - other [Member]
Assets:
Investments	$ 2,951	$ 3,098		$ 0	$ 2,640			$ 0	$ 0			$ 458	$ 0		$ 458	$ 2,640		$ 365	$ 2,586	$ 0	$ 2,586	$ 0	$ 0	$ 365	$ 0
Mark-to-market energy assets						0				385	0						385
Liabilities:
Mark-to-market energy liabilities			$ 0				$ 127							$ 127