Fair Value of Financial Instruments - Valuation Techniques And Unobservable Inputs (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2017 USD ($)
Level 3 | Minimum
Unobservable input
Loss severities (as a percent)	9.60%
Level 3 | Maximum
Unobservable input
Loss severities (as a percent)	98.30%
Level 3 | Weighted Average
Unobservable input
Discount rates (as a percent)	5.50%
Loss severities (as a percent)	41.90%
Probability of outcomes	33.20%
Securitized mortgage borrowings | Level 3
Valuation techniques
Estimated fair value of liabilities	$ (3,892,668)
Securitized mortgage borrowings | Level 3 | Minimum
Unobservable input
Default rates (as a percent)	0.03%
Securitized mortgage borrowings | Level 3 | Maximum
Unobservable input
Default rates (as a percent)	10.00%
Securitized mortgage borrowings | Level 3 | Weighted Average
Unobservable input
Default rates (as a percent)	1.70%
Securitized mortgage borrowings | DCF | Level 3 | Minimum
Unobservable input
Loss severities (as a percent)	4.00%
Securitized mortgage borrowings | DCF | Level 3 | Maximum
Unobservable input
Loss severities (as a percent)	25.00%
Long-term debt | DCF | Level 3
Valuation techniques
Estimated fair value of liabilities	$ (50,044)
Unobservable input
Discount rates (as a percent)	9.80%
Long-term debt | DCF | Level 3 | Weighted Average
Unobservable input
Discount rates (as a percent)	9.80%
Contingent consideration | Level 3 | Minimum
Unobservable input
Margins	2.30%
Contingent consideration | Level 3 | Maximum
Unobservable input
Margins	2.70%
Contingent consideration | Level 3 | Weighted Average
Unobservable input
Probability of outcomes	2.50%
Contingent consideration | LIBOR | Minimum
Unobservable input
Probability of outcomes	25.00%
Contingent consideration | LIBOR | Maximum
Unobservable input
Probability of outcomes	50.00%
Contingent consideration | DCF | Level 3
Valuation techniques
Estimated fair value of liabilities	$ (24,498)
Unobservable input
Margins	13.50%
Contingent consideration | DCF | Level 3 | Weighted Average
Unobservable input
Margins	13.50%
Securitized mortgage collateral | DCF | Level 3
Valuation techniques
Estimated fair value of assets	$ 3,903,336
Securitized mortgage collateral | DCF | Level 3 | Minimum
Unobservable input
Prepayment rates (as a percent)	2.50%
Securitized mortgage collateral | DCF | Level 3 | Maximum
Unobservable input
Prepayment rates (as a percent)	30.50%
Securitized mortgage collateral | DCF | Level 3 | Weighted Average
Unobservable input
Prepayment rates (as a percent)	7.20%
Mortgage servicing rights | DCF | Level 3
Valuation techniques
Estimated fair value of assets	$ 141,586
Mortgage servicing rights | DCF | Level 3 | Minimum
Unobservable input
Discount rates (as a percent)	9.00%
Prepayment rates (as a percent)	8.00%
Mortgage servicing rights | DCF | Level 3 | Maximum
Unobservable input
Discount rates (as a percent)	14.00%
Mortgage servicing rights | DCF | Level 3 | Weighted Average
Unobservable input
Discount rates (as a percent)	9.50%
Prepayment rates (as a percent)	9.30%
Mortgage servicing rights | Derivative liabilities, net, securitized trusts | DCF | Level 3 | Maximum
Unobservable input
Prepayment rates (as a percent)	86.60%
Interest rate lock commitments. net (IRLCs) | Market pricing | Level 3
Valuation techniques
Estimated fair value of assets	$ 12,333
Interest rate lock commitments. net (IRLCs) | Market pricing | Level 3 | Minimum
Unobservable input
Pull-through rate (as a percent)	24.10%
Interest rate lock commitments. net (IRLCs) | Market pricing | Level 3 | Maximum
Unobservable input
Pull-through rate (as a percent)	99.90%
Interest rate lock commitments. net (IRLCs) | Market pricing | Level 3 | Weighted Average
Unobservable input
Pull-through rate (as a percent)	78.60%