Derivatives and Hedging Activities - Schedule of Notional Amounts of Outstanding Derivative Positions (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended	9 Months Ended
	Sep. 30, 2021	Jun. 30, 2021	Jun. 30, 2020	Sep. 30, 2021	Dec. 31, 2020
Derivative Assets (included in other assets on the consolidated balance sheets):
Derivative Asset, Notional Amount	$ 1,368.8			$ 1,368.8	$ 901.6
Derivative Asset, Estimated Fair Value	34.1			34.1	55.3
Derivative Liabilities (included in accounts payable and accrued expenses on the consolidated balance sheets):
Derivative Liabilities, Notional Amount	$ 1,442.4			1,442.4	1,014.1
Derivative Liabilities, Estimated Fair Value					17.9
Payments for (Proceeds from) Derivative Instrument, Investing Activities			$ 500.0	200.0
Derivatives, Basis and Use of Derivatives	99	87
Interest rate swap contracts
Derivative Assets (included in other assets on the consolidated balance sheets):
Derivative Asset, Notional Amount	$ 587.6			587.6	87.6
Derivative Asset, Estimated Fair Value	0.4			0.4	0.2
Not Designated as Hedging Instrument | Interest rate swap contracts
Derivative Assets (included in other assets on the consolidated balance sheets):
Derivative Asset, Notional Amount	854.8			854.8	799.7
Derivative Asset, Estimated Fair Value	27.5			27.5	52.0
Derivative Liabilities (included in accounts payable and accrued expenses on the consolidated balance sheets):
Derivative Liabilities, Notional Amount	854.8			854.8	799.7
Derivative Liabilities, Estimated Fair Value	20.7			20.7	16.6
Not Designated as Hedging Instrument | Interest rate lock commitments
Derivative Assets (included in other assets on the consolidated balance sheets):
Derivative Asset, Notional Amount	149.8			149.8	101.9
Derivative Asset, Estimated Fair Value	3.1			3.1	3.3
Not Designated as Hedging Instrument | Forward loan sales contracts
Derivative Assets (included in other assets on the consolidated balance sheets):
Derivative Asset, Notional Amount		$ 164.2			0.0
Derivative Liabilities (included in accounts payable and accrued expenses on the consolidated balance sheets):
Derivative Liabilities, Notional Amount	0.0			0.0	126.8
Derivative Liabilities, Estimated Fair Value	0.0			0.0	1.1
Designated as Hedging Instrument [Member] | Interest rate swap contracts
Derivative Assets (included in other assets on the consolidated balance sheets):
Derivative Asset, Notional Amount	200.0			200.0	0.0
Derivative Asset, Estimated Fair Value	$ 2.6			$ 2.6	$ 0.0