Bank Note Payable and Term Note Payable (Details) $ in Thousands		9 Months Ended
	Sep. 27, 2012 USD ($)	Sep. 30, 2018 USD ($) period	Aug. 02, 2018 USD ($)	Dec. 31, 2017 USD ($)
Debt Instrument [Line Items]
Borrowings outstanding		$ 17,000		$ 78,000
Senior Notes
Debt Instrument [Line Items]
Principal amount of loan		$ 200,000
Fixed charge coverage ratio		1.50
Series A Notes
Debt Instrument [Line Items]
Principal amount of loan		$ 116,000
Interest rate (as a percent)		3.99%
Series B Notes
Debt Instrument [Line Items]
Principal amount of loan		$ 84,000
Interest rate (as a percent)		4.26%
Maximum | Senior Notes
Debt Instrument [Line Items]
Unsecured leverage ratio		60.00%
Unsecured leverage ratio for significant acquisition		65.00%
BAML Revolver
Debt Instrument [Line Items]
Weighted average interest rate (as a percent)		3.07%
Effective interest rate (as a percent)		3.33%		2.63%
Total available		$ 600,000
Number of periods of extension | period		2
Length of extension period		6 months
Additional borrowing capacity allowed by exercising an accordion feature		$ 500,000
Borrowings outstanding		$ 17,000		$ 78,000
Facility fee at period end (as a percent)		0.25%
BAML Revolver | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		1.20%
BAML Revolver | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		0.20%
BAML Term Loan
Debt Instrument [Line Items]
Principal amount of loan		$ 400,000
Effective interest rate (as a percent)		2.47%
Additional borrowing capacity allowed by exercising an accordion feature		$ 500,000
Amount drawn down	$ 400,000
BAML Term Loan | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		1.35%
Fixed rate (as a percent)		1.12%
BAML Term Loan | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		0.35%
JPM Term Loan
Debt Instrument [Line Items]
Principal amount of loan			$ 150,000
Interest rate during period (as a percent)		3.38%
Weighted average interest rate (as a percent)		3.24%		2.45%
JPM Term Loan | Eurodollar Rate
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		1.25%
JPM Term Loan | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		0.25%
BMO Term Loan
Debt Instrument [Line Items]
Principal amount of loan		$ 220,000
Additional loans allowed by exercising an accordion feature		$ 100,000
Effective interest rate (as a percent)		3.57%
BMO Term Loan | LIBOR
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		1.25%
Fixed rate (as a percent)		2.32%
BMO Term Loan | Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate at period end (as a percent)		0.25%
Tranche A Term Loan
Debt Instrument [Line Items]
Principal amount of loan		$ 55,000
Tranche B Term Loan
Debt Instrument [Line Items]
Principal amount of loan		$ 165,000