Indebtedness - Additional Information (Detail) (USD $)	12 Months Ended	0 Months Ended	9 Months Ended	0 Months Ended		1 Months Ended	2 Months Ended
	Dec. 31, 2014	Dec. 09, 2014	Dec. 31, 2014	Jul. 05, 2011	Apr. 14, 2014	Dec. 31, 2002 Property	Nov. 30, 2004 Property	Dec. 31, 2013	Apr. 12, 2014
Debt Instrument [Line Items]
Lease term	15 years
Debt	$ 606,082,000		606,082,000					$ 142,704,000
Weighted-average borrowing rate on bonds	0.24%		0.24%					0.25%
Through December 31, 2015
Debt Instrument [Line Items]
Debt covenant, EBITDA plus lease expense to fixed charges	1.75
Debt covenant, total debt to EBITDA	3.25
Thereafter
Debt Instrument [Line Items]
Debt covenant, EBITDA plus lease expense to fixed charges	2.00
Debt covenant, total debt to EBITDA	3.00
Minimum
Debt Instrument [Line Items]
Lease renewal option term	1 year
Maximum
Debt Instrument [Line Items]
Lease renewal option term	20 years
Line of Credit
Debt Instrument [Line Items]
Debt	69,116,000		69,116,000					0
Line of Credit | Credit Facility, 2014 | Term Loan
Debt Instrument [Line Items]
Line of credit amount outstanding					126,300,000
Line of credit, additional borrowing capacity		1,900,000
Equal quarterly installments		3,100,000
Line of Credit | Credit Facility, 2014 | Revolving Credit Agreement
Debt Instrument [Line Items]
Line of credit amount outstanding	155,900,000		155,900,000
Line of credit, current borrowing capacity		225,000,000.0			200,000,000.0				140,000,000.0
Line of credit, additional borrowing capacity		200,000,000.0
Line of Credit | Credit Facility, 2014 | Revolving Credit Agreement | Minimum
Debt Instrument [Line Items]
Commitment fee for unused balance amount			0.15%
Line of Credit | Credit Facility, 2014 | Revolving Credit Agreement | Maximum
Debt Instrument [Line Items]
Commitment fee for unused balance amount			0.30%
Line of Credit | Credit Facility, 2014 | Subfacility
Debt Instrument [Line Items]
Line of credit, current borrowing capacity					20,000,000.0				10,000,000.0
Line of Credit | Credit Facility, 2014 | Swingline Loan Subfacility
Debt Instrument [Line Items]
Line of credit, current borrowing capacity					25,000,000.0				15,000,000.0
Line of Credit | Credit Facility, 2014 | LIBOR | Revolving Credit Agreement | Minimum
Debt Instrument [Line Items]
Interest rate basis spread			1.75%
Line of Credit | Credit Facility, 2014 | LIBOR | Revolving Credit Agreement | Maximum
Debt Instrument [Line Items]
Interest rate basis spread			2.25%
Weighted-average borrowing rate on bonds	2.16%		2.16%
Senior Unsecured Notes Issued July 2011
Debt Instrument [Line Items]
Notes issued				125,000,000
Payment of Interest, commencement date				Jul. 27, 2011
Annual principal repayment amount				25,000,000
Debt principal amount, commencement date				Apr. 27, 2014
Debt interest rate				3.95%
Senior Notes | Senior Unsecured Notes, 4.75 Note Due 2021
Debt Instrument [Line Items]
Notes issued					300,000,000.0
Debt interest rate					4.75%
Periodic payment, principal					60,000,000.0
Debt	300,000,000		300,000,000					0
Related Party
Debt Instrument [Line Items]
Number of capital leases	19		19
Properties sold						10	11
Borrowings collateralized by the land and buildings						5,000,000	6,800,000
Lease term						15 years	15 years
Lease renewal option term							5 years
Aggregate annual rental						$ 1,227,000	$ 788,000
Interest implicit in the leases						10.10%	9.70%