Derivative Instruments - Summary of Derivative Instruments (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Derivatives
Notional Amount	$ 5,837,562
Derivative Assets	137,394	$ 15,250
Derivative Liabilities	103,564	4,356
Derivative asset netting	(2,152)	(6,982)
Derivative liability netting	(93,785)	(991)
Total derivative assets, net	135,242	8,268
Total derivative liabilities, net	9,779	3,365
Other assets
Derivatives
Derivative Assets	137,394	15,250
Derivative asset netting	(2,152)	(6,982)
Total derivative assets, net	135,242	8,268
Accrued expenses and other liabilities
Derivatives
Derivative Liabilities	103,564	4,356
Derivative liability netting	(93,785)	(991)
Total derivative liabilities, net	9,779	3,365
Derivatives designated as hedges
Derivatives
Notional Amount	321,075	307,271
Derivatives designated as hedges | Other assets
Derivatives
Derivative Assets	1,252	3,373
Derivatives designated as hedges | Accrued expenses and other liabilities
Derivatives
Derivative Liabilities	11	0
Derivatives not designated as hedges
Derivatives
Notional Amount	5,516,487	1,390,750
Derivatives not designated as hedges | Other assets
Derivatives
Derivative Assets	136,142	11,877
Derivatives not designated as hedges | Accrued expenses and other liabilities
Derivatives
Derivative Liabilities	103,553	4,356
Interest rate contracts
Derivatives
Derivative Assets	130,391	7,909
Derivative Liabilities	101,910	3,732
Derivative asset netting	(312)	(395)
Derivative liability netting	(93,099)	(395)
Total derivative assets, net	130,079	7,514
Total derivative liabilities, net	8,811	3,337
Interest rate contracts | Derivatives designated as hedges
Derivatives
Notional Amount	150,000	150,000
Interest rate contracts | Derivatives designated as hedges | Other assets
Derivatives
Derivative Assets	0	393
Interest rate contracts | Derivatives designated as hedges | Accrued expenses and other liabilities
Derivatives
Derivative Liabilities	11	0
Interest rate contracts | Derivatives not designated as hedges
Derivatives
Notional Amount	4,694,964	1,095,449
Interest rate contracts | Derivatives not designated as hedges | Other assets
Derivatives
Derivative Assets	130,391	7,516
Interest rate contracts | Derivatives not designated as hedges | Accrued expenses and other liabilities
Derivatives
Derivative Liabilities	101,899	3,732
Forward foreign exchange contracts
Derivatives
Derivative Assets	1,666	6,689
Derivative Liabilities	315	13
Derivative asset netting	(1,666)	(6,587)
Derivative liability netting	(156)	(13)
Total derivative assets, net	0	102
Total derivative liabilities, net	159	0
Forward foreign exchange contracts | Derivatives designated as hedges
Derivatives
Notional Amount	171,075	157,271
Forward foreign exchange contracts | Derivatives designated as hedges | Other assets
Derivatives
Derivative Assets	1,252	2,980
Forward foreign exchange contracts | Derivatives designated as hedges | Accrued expenses and other liabilities
Derivatives
Derivative Liabilities	0	0
Forward foreign exchange contracts | Derivatives not designated as hedges
Derivatives
Notional Amount	291,999	254,274
Forward foreign exchange contracts | Derivatives not designated as hedges | Other assets
Derivatives
Derivative Assets	414	3,709
Forward foreign exchange contracts | Derivatives not designated as hedges | Accrued expenses and other liabilities
Derivatives
Derivative Liabilities	315	13
Interest rate lock commitments
Derivatives
Derivative Assets	4,554	652
Derivative Liabilities	113	28
Derivative asset netting	(8)	0
Derivative liability netting	(8)	0
Total derivative assets, net	4,546	652
Total derivative liabilities, net	105	28
Interest rate lock commitments | Derivatives not designated as hedges
Derivatives
Notional Amount	266,949	28,007
Interest rate lock commitments | Derivatives not designated as hedges | Other assets
Derivatives
Derivative Assets	4,554	652
Interest rate lock commitments | Derivatives not designated as hedges | Accrued expenses and other liabilities
Derivatives
Derivative Liabilities	113	28
Forward loan sales commitments
Derivatives
Derivative Assets	166
Derivative Liabilities	253
Derivative asset netting	(166)
Derivative liability netting	(166)
Total derivative assets, net	0
Total derivative liabilities, net	87
Forward loan sales commitments | Derivatives not designated as hedges
Derivatives
Notional Amount	218,061
Forward loan sales commitments | Derivatives not designated as hedges | Other assets
Derivatives
Derivative Assets	166
Forward loan sales commitments | Derivatives not designated as hedges | Accrued expenses and other liabilities
Derivatives
Derivative Liabilities	253
Power Equity CDs
Derivatives
Derivative Assets	617
Derivative Liabilities	617
Derivative asset netting	0
Derivative liability netting	0
Total derivative assets, net	617
Total derivative liabilities, net	617
Power Equity CDs | Derivatives not designated as hedges
Derivatives
Notional Amount	31,870
Power Equity CDs | Derivatives not designated as hedges | Other assets
Derivatives
Derivative Assets	617
Power Equity CDs | Derivatives not designated as hedges | Accrued expenses and other liabilities
Derivatives
Derivative Liabilities	617
Swap agreement
Derivatives
Derivative Liabilities	356	583
Derivative liability netting	(356)	(583)
Total derivative liabilities, net	0	0
Swap agreement | Derivatives not designated as hedges
Derivatives
Notional Amount	12,644	13,020
Swap agreement | Derivatives not designated as hedges | Other assets
Derivatives
Derivative Assets	0	0
Swap agreement | Derivatives not designated as hedges | Accrued expenses and other liabilities
Derivatives
Derivative Liabilities	$ 356	$ 583