Commercial Mortgage Banking - Summary of Changes in Carrying Value of Mortgage Servicing Rights (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015		Mar. 31, 2014
Transfers and Servicing [Abstract]
Balance at beginning of period	$ 30,140		$ 28,879
Originations	601	[1]	1,544	[1]
Purchases	208		21
Disposals	(2,328)	[1]	(562)	[1]
Amortization expense	(230)		(656)
Balance at end of period	$ 28,391		$ 29,226

[1] Includes refinancings