Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011	Apr. 30, 2013
Summary Of Significant Accounting Policies [Line Items]
Assets held for sale	$ 0	$ 0
Non current restricted investments	209,990,000
Impairments of goodwill	0	0	0
Insurance coverage of general liability and auto liability risks	100,000,000			100,000,000
Insurance policy covering pollution liability	50,000,000
Tax benefit recognized	Greater than 50%
US Treasury [Member]
Summary Of Significant Accounting Policies [Line Items]
Non current restricted investments	130,000,000
Original maturity period	13 weeks
CD [Member]
Summary Of Significant Accounting Policies [Line Items]
Original maturity period	No longer than approximately 26 weeks.
Balance in excess of FDIC-insured limits	80,000,000
Cash and Cash Equivalents [Member]
Summary Of Significant Accounting Policies [Line Items]
Balance in excess of FDIC-insured limits	600,000
Non Current Restricted Cash [Member]
Summary Of Significant Accounting Policies [Line Items]
Balance in excess of FDIC-insured limits	49,800,000
Noncurrent Restricted Cash [Member] | CD [Member]
Summary Of Significant Accounting Policies [Line Items]
Balance in excess of FDIC-insured limits	$ 79,800,000
Minimum [Member]
Summary Of Significant Accounting Policies [Line Items]
Ownership interest in equity method investment	20.00%
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Ownership interest in equity method investment	50.00%