Debt - Additional Information (Detail)			3 Months Ended		9 Months Ended
	Aug. 05, 2015 USD ($) extension_option	May. 30, 2014 USD ($) promissory_note	Sep. 30, 2015 USD ($) property	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) extension_option property	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)	Oct. 31, 2009 promissory_note	Oct. 01, 2009 USD ($)
Line of Credit Facility [Line Items]
Debt outstanding			$ 400,700,000		$ 400,700,000		$ 358,200,000
Unsecured revolving credit facility			45,000,000		45,000,000		0
Mortgage notes payable			95,696,000		95,696,000		98,205,000
Interest expense			7,221,000	$ 5,943,000	19,111,000	$ 15,722,000
Amortization of deferred financing costs			500,000	500,000	1,600,000	1,000,000
Write-off of deferred financing costs					1,208,000	0
Amortization of debt discount				0		51,000
Interest payable			5,700,000		5,700,000		$ 1,700,000
Interest Rate Swap [Member]
Line of Credit Facility [Line Items]
Loss on settlement of interest rate swap				$ 1,700,000		$ 1,700,000
Ensign [Member]
Line of Credit Facility [Line Items]
Debt outstanding			359,512,000		359,512,000
General Electric Capital Corporation [Member]
Line of Credit Facility [Line Items]
Advances included in mortgage note payable					49,200,000
General Electric Capital Corporation [Member] | Mortgage Notes Payable due May 30, 2017 [Member]
Line of Credit Facility [Line Items]
Debt instrument, face amount			$ 46,500,000		$ 46,500,000
Debt instrument, maturity date					May 30, 2017
Number of properties subject to mortgage loans | property			10		10
Mortgage notes payable			$ 95,700,000		$ 95,700,000
Advances included in mortgage note payable		$ 50,700,000
Debt instrument, interest rate terms					This advance bears interest at a floating rate equal to three month LIBOR plus 3.35%, reset monthly and subject to a LIBOR floor of 0.50%, with monthly principal and interest payments based on a 25 year amortization.
Debt instrument payment amortization period					25 years
Debt instrument blended interest rate					7.25%
Debt instrument, number of extension options | extension_option					2
Debt instrument, extension options period					12 months
Extension fees equal percent on outstanding principal balance			0.25%		0.25%
Notice period for prepayments without penalty					30 days
General Electric Capital Corporation [Member] | Mortgage Notes Payable due May 30, 2017 [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread					0.50%
General Electric Capital Corporation [Member] | Mortgage Notes Payable due May 30, 2017 [Member] | Floating Rate [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread					3.35%
Johnson Land Enterprises, LLC [Member] | Promissory Notes September 30, 2019 [Member]
Line of Credit Facility [Line Items]
Debt instrument, face amount									$ 10,000,000.0
Number of promissory notes | promissory_note								4
Number of promissory notes repaid | promissory_note		3
Senior Unsecured Notes [Member]
Line of Credit Facility [Line Items]
Debt instrument, face amount		$ 260,000,000.0
Debt instrument, interest rate		5.875%	5.875%		5.875%
Proceeds from the issuance of senior unsecured notes payable		$ 260,000,000
Net proceeds from issuance of notes		$ 253,000,000
Debt instrument, maturity date					Jun. 01, 2021
Frequency of interest payable on notes					Interest on the Notes is payable on June 1 and December 1 of each year, beginning on December 1, 2014.
Debt instrument, early redeemable date					Jun. 01, 2017
Debt instrument, redemption price, percentage		100.00%
Debt instrument, redemption price, percentage upon change of control		101.00%
Senior Unsecured Notes [Member] | Ensign [Member]
Line of Credit Facility [Line Items]
Approximate amount transferred from net proceeds		$ 220,800,000
Senior Unsecured Notes [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Percentage of aggregate principal amount of notes outstanding		65.00%
Senior Unsecured Notes [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Redeemable percentage of aggregate principal amount of notes		35.00%
Line of Credit [Member] | Unsecured Asset-Based Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, borrowing capacity	$ 300,000,000.0
Unsecured revolving credit facility	$ 45,000,000
Number of extension options | extension_option	2
Line of credit facility, extension period	6 months
Line of credit facility, additional borrowing capacity	$ 200,000,000
Line of Credit [Member] | Unsecured Asset-Based Revolving Credit Facility [Member] | Minimum [Member]
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee percentage	0.15%
Line of credit facility, facility fee percentage	0.125%
Line of Credit [Member] | Unsecured Asset-Based Revolving Credit Facility [Member] | Minimum [Member] | LIBOR [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread	1.75%
Line of Credit [Member] | Unsecured Asset-Based Revolving Credit Facility [Member] | Minimum [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread	0.75%
Line of Credit [Member] | Unsecured Asset-Based Revolving Credit Facility [Member] | Maximum [Member]
Line of Credit Facility [Line Items]
Line of credit facility, commitment fee percentage	0.25%
Line of credit facility, facility fee percentage	0.30%
Line of Credit [Member] | Unsecured Asset-Based Revolving Credit Facility [Member] | Maximum [Member] | LIBOR [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread	2.40%
Line of Credit [Member] | Unsecured Asset-Based Revolving Credit Facility [Member] | Maximum [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Debt instrument, basis spread	1.40%
Line of Credit [Member] | Senior Secured Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Line of credit facility, borrowing capacity		$ 150,000,000.0
Line of credit facility, additional borrowing capacity		$ 75,000,000.0