Acquisitions and Divestitures - Merger and Integration Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Business Acquisition [Line Items]
Merger and integration expense	$ 8,647	$ 43,116	$ 14,307	$ 74,490
Professional fees
Business Acquisition [Line Items]
Merger and integration expense	4,478	8,991	6,345	14,624
Employee compensation, incentives and benefits
Business Acquisition [Line Items]
Merger and integration expense	1,472	3,849	2,989	9,086
Contract employment and outsourcing
Business Acquisition [Line Items]
Merger and integration expense	17	1,703	17	3,102
Occupancy
Business Acquisition [Line Items]
Merger and integration expense	1,505	2,229	1,623	2,259
Miscellaneous expense
Business Acquisition [Line Items]
Merger and integration expense	79	3,099	1,148	5,133
All other expense
Business Acquisition [Line Items]
Merger and integration expense	$ 1,096	$ 23,245	$ 2,185	$ 40,286