Related Party Transactions - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Related Party Transactions [Abstract]
Allocations of expenses for general and administrative services	$ 0	$ 5,500,000	$ 0	$ 7,400,000
Rental income from related party	2,308,000	4,700,000	16,308,000	4,700,000
Tenant reimbursements from related party	200,000	$ 400,000	1,406,000	400,000
Account receivable due from related party for tenant reimbursement	$ 0		0		$ 2,275,000
Net contribution from (distribution to) Ensign			$ 0	$ 4,356,000