Acquisition (Narrative) (Details) - USD ($) $ in Thousands		3 Months Ended
	Sep. 01, 2017	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Business Acquisition [Line Items]
Cash payment to acquire business		$ 0	$ 0
Proceeds from issuance of Class A convertible preferred units, net		0
6.500% Senior Unsecured Notes Due October 2025
Business Acquisition [Line Items]
Debt issued		$ 550,000		$ 550,000
Senior unsecured notes, stated rate		6.50%		6.50%
Class A Convertible Preferred Stock Units | Private Placement
Business Acquisition [Line Items]
Temporary Equity, Stock Issued During Period, Value, New Issues	$ 750,000
Alkali Business
Business Acquisition [Line Items]
Cash payment to acquire business	1,325,000
Working capital included in cash payment to acquire business	105,000
Alkali Business | 6.500% Senior Unsecured Notes Due October 2025
Business Acquisition [Line Items]
Debt issued	$ 550,000
Senior unsecured notes, stated rate	6.50%
Proceeds from issuance of unsecured debt	$ 540,100
Alkali Business | Class A Convertible Preferred Stock Units | Private Placement
Business Acquisition [Line Items]
Temporary Equity, Stock Issued During Period, Value, New Issues	750,000
Proceeds from issuance of Class A convertible preferred units, net	$ 726,200