Acquisitions and Divestitures - Merger and Integration Expenses (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Business Acquisition [Line Items]
Merger and integration expense	$ 5,660	$ 31,374
Professional fees
Business Acquisition [Line Items]
Merger and integration expense	1,867	5,633
Employee compensation, incentives and benefits
Business Acquisition [Line Items]
Merger and integration expense	1,517	5,237
Contract employment and outsourcing
Business Acquisition [Line Items]
Merger and integration expense	0	1,399
Miscellaneous expense
Business Acquisition [Line Items]
Merger and integration expense	1,187	2,064
All other expense
Business Acquisition [Line Items]
Merger and integration expense	$ 1,089	$ 17,041