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Borrowings - Schedule of Long-term Borrowings (Details) - USD ($) $ in Thousands		12 Months Ended
	Aug. 01, 2019	Dec. 31, 2019	Dec. 31, 2018
Debt Instrument [Line Items]
Current Fiscal Year End Date		--12-31
FHLB advances		$ 1,500,000
Long-term debt, gross		428,470	$ 253,391
Discounted lease rentals		100,882	92,976
Total long-term borrowings		2,354,448	1,449,472
Debt premium		12,100
Debt discount		(1,600)
2020		315,100
2021		1,321,934
2022		146,005
2023		26,308
2024		11,003
Thereafter		534,098
Total long-term borrowings		2,354,448
FHLB advances due 2020 to 2025
Debt Instrument [Line Items]
FHLB advances		1,822,058	1,100,000
FHLB advances, current		110,000
Advances payable		$ 1,810,000
FHLB advances due 2020 to 2025 \| Minimum
Debt Instrument [Line Items]
Stated Rate		1.30%
FHLB advances due 2020 to 2025 \| Maximum
Debt Instrument [Line Items]
Stated Rate		2.72%
Subordinated debt securities due 2032-2035
Debt Instrument [Line Items]
Long-term debt, gross		$ 20,600
Discounted lease rentals due 2020 to 2024 \| Minimum
Debt Instrument [Line Items]
Stated Rate		2.64%
Discounted lease rentals due 2020 to 2024 \| Maximum
Debt Instrument [Line Items]
Stated Rate		6.50%
Finance lease obligation due 2038
Debt Instrument [Line Items]
Stated Rate		3.73%
Finance lease obligation		$ 3,038	3,105
Subordinated bank notes
Debt Instrument [Line Items]
Hedge related adjustment		$ 2,773	(4,165)
Subordinated bank notes \| Subordinated debt obligation due 2022
Debt Instrument [Line Items]
Stated Rate		6.25%
Long-term debt, gross		$ 109,338	109,095
Subordinated bank notes \| Subordinated debt obligation due 2025
Debt Instrument [Line Items]
Stated Rate		4.60%
Long-term debt, gross		$ 148,681	148,461
Subordinated bank notes \| Subordinated debt obligation due 2029
Debt Instrument [Line Items]
Stated Rate		4.13%
Long-term debt, gross		$ 148,657	0
Subordinated bank notes \| Subordinated debt securities due 2032-2035
Debt Instrument [Line Items]
Long-term debt, gross		$ 19,021	$ 0
Subordinated bank notes \| Subordinated debt securities due 2032-2035 \| Minimum
Debt Instrument [Line Items]
Stated Rate		3.54%
Subordinated bank notes \| Subordinated debt securities due 2032-2035 \| Maximum
Debt Instrument [Line Items]
Stated Rate		5.34%
Subordinated bank notes \| Three-Month LIBOR \| Subordinated debt securities due 2032-2035 \| Minimum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		1.45%
Subordinated bank notes \| Three-Month LIBOR \| Subordinated debt securities due 2032-2035 \| Maximum
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate		3.25%
Subordinated bank notes \| Three-Month LIBOR \| Subordinated Bank Notes Due 2032
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	3.25%