Debt - Credit Facilities (Details)	1 Months Ended				3 Months Ended		9 Months Ended
	Aug. 31, 2016 USD ($) extension_option	Jul. 31, 2016 USD ($)	Jun. 30, 2016	Sep. 30, 2013 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2016 USD ($)	Sep. 30, 2015 USD ($)	Dec. 31, 2015 USD ($)	Mar. 31, 2013 USD ($)
Line of Credit Facility [Line Items]
Revolving credit facilities					$ 75,000,000		$ 75,000,000		$ 0
Loss on early extinguishment of debt					13,408,000	$ 0	13,408,000	$ 0
Debt outstanding					2,926,821,000		2,926,821,000		2,524,395,000
Senior Secured Revolving Credit Facility
Line of Credit Facility [Line Items]
Credit facility amount, maximum				$ 800,000,000	650,000,000		650,000,000			$ 500,000,000
Revolving credit facilities					75,000,000		75,000,000		0
Loss on early extinguishment of debt					2,700,000
Until March 2017 | LIBOR | Senior Secured Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate				2.75%
March 2017 and Thereafter | LIBOR | Senior Secured Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate				3.125%
Line of Credit | Revolving Credit Facility
Line of Credit Facility [Line Items]
Credit facility amount, maximum	$ 650,000,000.0
Revolving credit facilities					$ 75,000,000		$ 75,000,000
Repayments of borrowings on existing credit facility		$ 142,000,000
Debt instrument extension period (up to)	1 year
Line of Credit | LIBOR | Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate							1.85%
Series E Perpetual Preferred Shares
Line of Credit Facility [Line Items]
Preferred stock, dividend rate, percentage		6.35%	6.35%		6.35%		6.35%
Credit Agreement
Line of Credit Facility [Line Items]
Total credit agreement amount	$ 1,000,000,000.0
Credit agreement accordion feature (not to exceed)	1,750,000,000
Delayed Draw Term Loan Facility
Line of Credit Facility [Line Items]
Secured debt outstanding					$ 246,575,000		$ 246,575,000		$ 0
Delayed Draw Term Loan Facility | Secured Debt
Line of Credit Facility [Line Items]
Credit facility amount, maximum	$ 350,000,000.0
Debt instrument extension period (up to)	1 year
Number of extension options | extension_option	2
Secured debt outstanding					$ 250,000,000		$ 250,000,000
Delayed Draw Term Loan Facility | Secured Debt | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate							1.80%
Minimum | Line of Credit | LIBOR | Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.75%
Minimum | Line of Credit | Base Rate | Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	0.75%
Minimum | Delayed Draw Term Loan Facility | Secured Debt | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.70%
Minimum | Delayed Draw Term Loan Facility | Secured Debt | Base Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	0.70%
Maximum | Line of Credit | LIBOR | Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.30%
Maximum | Line of Credit | Base Rate | Revolving Credit Facility
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.30%
Maximum | Delayed Draw Term Loan Facility | Secured Debt | LIBOR
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	2.30%
Maximum | Delayed Draw Term Loan Facility | Secured Debt | Base Rate
Line of Credit Facility [Line Items]
Debt instrument, basis spread on variable rate	1.30%