Income Taxes Income Taxes (Tables) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended		12 Months Ended
	Mar. 31, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Effective Income Tax Rate Reconciliation, Percent		25.20%	33.50%
U.S. federal statutory rate	35.00%	21.00%	35.00%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities		$ (98,521)		$ (65,087)
Tax Cuts and Jobs Act of 2017, transition tax for accumulated foreign earnings, provisional amount				51,000
Tax Cuts and Jobs Act of 2017, tax benefit from decrease to net deferred tax liabilities, provisional amount				$ 73,000
Stahlgruber [Member]
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Deferred Tax Liabilities		$ (97,805)