Fair Value of Financial Instruments Measured at Fair Value - Additional Information about Servicing Assets and Liabilities Measured at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014	Dec. 31, 2014
Servicing Assets, Changes in fair value due to:
Fair value at December 31,			$ 2,181
Fair value at March 31,	3,496		2,181
Servicing Liabilities, Changes in fair value due to:
Fair value at December 31,			3,973
Fair value at March 31,	4,397		3,973
Fair Value, Measurements, Recurring
Servicing Assets, Changes in fair value due to:
Fair value at December 31,	2,181	534
Additions, included in other/deferred revenue	1,508	442
Changes in fair value, included in servicing fees	(491)	(112)
Fair value at March 31,	3,496	864
Servicing Liabilities, Changes in fair value due to:
Fair value at December 31,	3,973	936
Additions, included in other/deferred revenue	1,412	512
Changes in fair value, included in servicing fees	(988)	(227)
Fair value at March 31,	4,397	1,221
Deferred Revenue | Fair Value, Measurements, Recurring
Servicing Assets, Changes in fair value due to:
Additions, included in other/deferred revenue	298	0
Servicing Liabilities, Changes in fair value due to:
Additions, included in other/deferred revenue	$ 0	$ 0