Equity and Capital Equity and Capital - Common Stock (Details)	3 Months Ended
	Mar. 31, 2018 USD ($) shares
Class of Stock [Line Items]
Stock Repurchase Program Expiration Date	Feb. 06, 2020
Maximum [Member]
Class of Stock [Line Items]
Equity Issuances, Common Shares Authorized for Issuance | shares	500,000,000
Parent Company [Member] | Common Stock [Member]
Class of Stock [Line Items]
Stock Repurchased and Retired During Period, Shares | shares	2,145,209
Stock Repurchased and Retired During Period, Value	$ (124,989,000)
Parent Company [Member] | Common Stock [Member] | Accumulated Other Comprehensive Income (Loss) [Member]
Class of Stock [Line Items]
Stock Repurchased and Retired During Period, Value	0
Parent Company [Member] | Common Stock [Member] | Average share price [Member]
Class of Stock [Line Items]
Stock Repurchased and Retired During Period, Value	$ 58.24