Summary of Preliminary Fair Values and Purchase Price Allocation at Acquisition Date of Assets Acquired and Liabilities Assumed (Parenthetical) (Detail) (Griffith Energy Services, Inc., USD $) In Millions, unless otherwise specified	Mar. 31, 2014
Griffith Energy Services, Inc.
Business Acquisition [Line Items]
Gross contractual receivable amount	$ 48.2
Contractual cash flows not expected to be collected	$ 1.7