Subsequent Events - Share Issuances (Details)		3 Months Ended		9 Months Ended
	Oct. 03, 2017 shares	Sep. 30, 2017 shares	Sep. 30, 2016	Sep. 30, 2017 shares	Dec. 31, 2016 shares
Subsequent Event [Line Items]
Preferred shares, shares outstanding (in shares)		47,810,000		47,810,000	37,010,000
5.0% Series A Participating Preferred Shares
Subsequent Event [Line Items]
Preferred stock, dividend rate, percentage		5.00%	5.00%	5.00%
5.0% Series B Participating Preferred Shares
Subsequent Event [Line Items]
Preferred stock, dividend rate, percentage		5.00%	5.00%	5.00%
Subsequent Event
Subsequent Event [Line Items]
Issuance of perpetual preferred shares, net of offering costs (in shares)	12,398,276
Class A conversion ratio	1.3106
Subsequent Event | 5.0% Series A Participating Preferred Shares
Subsequent Event [Line Items]
Preferred shares, shares outstanding (in shares)	5,060,000
Preferred stock, dividend rate, percentage	5.00%
Subsequent Event | 5.0% Series B Participating Preferred Shares
Subsequent Event [Line Items]
Preferred shares, shares outstanding (in shares)	4,400,000
Preferred stock, dividend rate, percentage	5.00%