Benefit Plans and Other Postretirement Benefits, Defined contribution plans (Details) - United States - USD ($) $ in Millions	6 Months Ended		12 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Defined Contribution Plan Disclosure
Contributions to U.S. defined contribution plans by the Company, maximum percentage of eligible compensation	6.00%		5.00%
Matching contributions to U.S. defined contribution plans by the Company	$ 7.2	$ 4.3