Acquisitions and Divestitures - Merger and Integration Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Business Acquisition [Line Items]
Merger and integration expense	$ 8,989	$ 11,349	$ 23,296	$ 85,839
Professional fees
Business Acquisition [Line Items]
Merger and integration expense	3,507	4,593	9,852	19,217
Employee compensation, incentives and benefits
Business Acquisition [Line Items]
Merger and integration expense	1,473	3,112	4,462	12,198
Contract employment and outsourcing
Business Acquisition [Line Items]
Merger and integration expense	223	599	240	3,701
Occupancy
Business Acquisition [Line Items]
Merger and integration expense	(76)	115	1,547	2,374
Miscellaneous expense
Business Acquisition [Line Items]
Merger and integration expense	1,022	1,381	2,170	6,514
All other expense
Business Acquisition [Line Items]
Merger and integration expense	$ 2,840	$ 1,549	$ 5,025	$ 41,835