Quarterly Financial Data - Additional Information (Detail) (USD $)	3 Months Ended			12 Months Ended			3 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012	Mar. 31, 2014
Quarterly Financial Data [Line Items]
Provision for long-term contract receivable	$ 49,900,000	$ 52,500,000		$ 102,460,000
Provision for long-term contract receivable, net of tax	30,300,000	32,300,000
Selling, general and administrative expenses				722,038,000	501,010,000	434,894,000
Gain on sale of equity ownership interest, Pre tax			112,700,000
Gain on sale of equity ownership interest, Net of tax			70,500,000
National Gas Company of Trinidad and Tobago Arbitration [Member]
Quarterly Financial Data [Line Items]
Selling, general and administrative expenses				38,800,000			38,800,000
Selling, general and administrative expenses, Net of tax							$ 25,800,000