Acquisitions - Schedule of Preliminary Fair Values of Assets Acquired and Liabilities Assumed (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2014	Dec. 31, 2013
Business Acquisition and Divestitures [Line Items]
Goodwill	$ 29,116	$ 9,324
PMI Acquisition [Member] | Preliminary Purchase Price Allocation [Member]
Business Acquisition and Divestitures [Line Items]
Accounts receivable	21,368
Inventory	19,040
Other current assets	2,903
Property and equipment	48,770
Intangible assets	15,000
Other noncurrent assets	210
Total identifiable assets	107,291
Accounts payable	36,310
Motor fuel taxes payable	303
Accrued expenses and other current liabilities	2,371
Deferred tax liabilities	18,787
Net identifiable assets	49,520
Goodwill	23,996
Net assets acquired	73,516
PMI Acquisition [Member] | Divestiture of Lubricants Business [Member]
Business Acquisition and Divestitures [Line Items]
Accounts receivable	2,038
Inventory	6,157
Other current assets	5
Property and equipment	4,437
Total identifiable assets	12,637
Accounts payable	2,864
Net identifiable assets	9,773
Goodwill	4,227
Net assets acquired	14,000
PMI Acquisition [Member] | Preliminary Purchase Price Allocation Net of Divestiture [Member]
Business Acquisition and Divestitures [Line Items]
Accounts receivable	19,330
Inventory	12,883
Other current assets	2,898
Property and equipment	44,333
Intangible assets	15,000
Other noncurrent assets	210
Total identifiable assets	94,654
Accounts payable	33,446
Motor fuel taxes payable	303
Accrued expenses and other current liabilities	2,371
Deferred tax liabilities	18,787
Net identifiable assets	39,747
Goodwill	19,769
Net assets acquired	59,516
Atlas Acquisition [Member] | Preliminary Purchase Price Allocation [Member]
Business Acquisition and Divestitures [Line Items]
Inventory	280
Property and equipment	21,735
Intangible assets	15,043
Other noncurrent assets	5,170
Total identifiable assets	42,228
Accrued expenses and other current liabilities	2,043
Net assets acquired	$ 40,185