Debt - Narrative (Details)			3 Months Ended		6 Months Ended
	May 10, 2017 USD ($)	Feb. 01, 2016 USD ($) extension_option	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2017 USD ($)	Aug. 05, 2015 USD ($)
Line of Credit Facility [Line Items]
Long-term Debt			$ 544,338,000		$ 544,338,000		$ 558,912,000
Outstanding amounts under Credit Facility			550,000,000		550,000,000		565,000,000
Interest expense			7,285,000	$ 6,219,000	14,377,000	$ 12,098,000
Amortization of deferred financing costs			500,000	$ 600,000	1,000,000	$ 1,100,000
Interest payable			1,400,000		1,400,000		1,400,000
Loss on extinguishment of debt before write off of deferred financing costs					7,600,000
Write off of deferred financing costs					4,200,000
Senior Unsecured Notes | 5.25% Senior Notes due 2025
Line of Credit Facility [Line Items]
Debt instrument, face amount	$ 300,000,000.0
Interest rate, stated percentage	5.25%
Gross proceeds from issuance of senior notes	$ 300,000,000
Net proceeds from issuance of senior notes	$ 294,000,000
Debt instrument, redemption price, percentage	100.00%
Debt instrument, redemption price, percentage upon change of control	101.00%
Senior Unsecured Notes | 5.25% Senior Notes due 2025 | Debt Instrument, Redemption, Period One
Line of Credit Facility [Line Items]
Debt instrument, redemption price, percentage	105.25%
Senior Unsecured Notes | 5.25% Senior Notes due 2025 | Debt Instrument, Redemption, Period One | Maximum
Line of Credit Facility [Line Items]
Debt instrument, redemption price, percentage of principal amount	40.00%
Senior Unsecured Notes | 5.25% Senior Notes due 2025 | Debt Instrument, Redemption, Period One | Minimum
Line of Credit Facility [Line Items]
Percentage of aggregate principal amount of notes outstanding	60.00%
Senior Unsecured Notes | 5.875% Senior Notes due 2021
Line of Credit Facility [Line Items]
Interest rate, stated percentage	5.875%
Payment for redemption of senior notes	$ 260,000,000
Debt instrument, redemption price, percentage	102.938%
Revolving Facility
Line of Credit Facility [Line Items]
Long-term Debt			150,000,000		150,000,000		165,000,000
Outstanding amounts under Credit Facility			$ 150,000,000		$ 150,000,000		$ 165,000,000
Revolving Facility | Unsecured Revolving Credit Facility
Line of Credit Facility [Line Items]
Line of credit facility, borrowing capacity								$ 300,000,000.0
Line of credit facility, accordion feature								$ 200,000,000.0
Revolving Facility | Unsecured Revolving Credit Facility | Maximum
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee percentage					0.25%
Line of credit facility, facility fee percentage					0.30%
Revolving Facility | Unsecured Revolving Credit Facility | Maximum | Base Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread					1.40%
Revolving Facility | Unsecured Revolving Credit Facility | Maximum | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, basis spread					2.40%
Revolving Facility | Unsecured Revolving Credit Facility | Minimum
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee percentage					0.15%
Line of credit facility, facility fee percentage					0.125%
Revolving Facility | Unsecured Revolving Credit Facility | Minimum | Base Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread					0.75%
Revolving Facility | Unsecured Revolving Credit Facility | Minimum | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, basis spread					1.75%
Revolving Facility | Revolving Credit Facility As Amended
Line of Credit Facility [Line Items]
Line of credit facility, borrowing capacity		$ 400,000,000.0
Line of credit facility, increase to borrowing capacity		100,000,000.0
Line of credit facility, increase to uncommitted incremental facility		50,000,000.0
Line of credit facility, uncommitted incremental facility limit		$ 250,000,000.0
Number of extension options | extension_option		2
Line of credit facility, extension period		6 months
Revolving Facility | Revolving Credit Facility As Amended | Maximum | Base Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread					1.60%
Revolving Facility | Revolving Credit Facility As Amended | Maximum | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, basis spread					2.60%
Revolving Facility | Revolving Credit Facility As Amended | Minimum | Base Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread					0.95%
Revolving Facility | Revolving Credit Facility As Amended | Minimum | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, basis spread					1.95%
Revolving Facility | Senior unsecured term loan
Line of Credit Facility [Line Items]
Line of credit facility, borrowing capacity		$ 100,000,000.0
Line of credit facility, prepayment premium in first year		2.00%
Line of credit facility, prepayment premium in second year		1.00%
Mortgage Notes Payable
Line of Credit Facility [Line Items]
Payments on the mortgage notes payable		$ 95,000,000