Fair Value of Assets and Liabilities - Additional Information about Servicing Assets and Liabilities Measured Using Different Market Servicing Rates and Different Prepayment (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted-average total market servicing rate assumptions	0.57%
Weighted-average base market servicing rate assumptions			0.50%
Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Weighted-average total market servicing rate assumptions	0.57%
Weighted-average base market servicing rate assumptions			0.50%
Changes in fair value, included in servicing fees	$ 232	$ (491)
Changes in fair value, included in servicing fees	(2,078)	$ (988)
Servicing rate increase by 0.10%
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Changes in fair value, included in servicing fees	$ (4,852)		$ (3,504)
Change in servicing rates	0.10%
Servicing rate increase by 0.10% | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Changes in fair value, included in servicing fees	$ 1,235		1,589
Servicing rate decrease by 0.10%
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Changes in fair value, included in servicing fees	$ 4,960		3,610
Change in servicing rates	(0.10%)
Servicing rate decrease by 0.10% | Fair Value, Measurements, Recurring
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Changes in fair value, included in servicing fees	$ (1,127)		$ (1,483)
Minimum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market servicing rates	0.57%		0.50%
Maximum
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Market servicing rates	0.90%		0.75%