Equity and Capital - Terms and Conditions of Preferred and Common Stock (Details)	1 Months Ended	12 Months Ended				24 Months Ended
	Feb. 26, 2018 USD ($)	Feb. 04, 2020	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares	Dec. 31, 2016 USD ($)	Feb. 06, 2020	Feb. 05, 2019 USD ($)	Feb. 07, 2018 USD ($)
Class of Stock [Line Items]
Amount avaiable for issuance			$ 500,000,000
Document Fiscal Year Focus			2018
Stock Repurchase Program, Number of Shares Authorized to be Repurchased								$ 250,000,000
Stock Repurchase Program Expiration Date						Feb. 06, 2020
Stock Repurchased During Period, Value	$ 246,500,000
Partnership Interest [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Issued | shares			0	0
Parent Company [Member]
Class of Stock [Line Items]
Preferred Stock, Shares Issued | shares			0	0
Net proceeds from common stock issuance			$ 0	$ 88,458,000	$ 548,920,000
Conversion of Stock, Conversion Ratio			0.45
Stock Issued During Period, Shares, Acquisitions | shares			65,500,000
Maximum [Member]
Class of Stock [Line Items]
Amount avaiable for issuance			$ 500,000,000
Subsequent Event [Member]
Class of Stock [Line Items]
Stock Repurchase Program, Number of Shares Authorized to be Repurchased							$ 250,000,000
Stock Repurchase Program Expiration Date		Feb. 04, 2020