Commercial Mortgage Banking - Summary of Changes in Carrying Value of Mortgage Servicing Rights (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Servicing Asset at Amortized Cost, Balance [Roll Forward]
Balance at beginning of year		$ 28,168	$ 30,140
Originations	[1]	2,575	6,569
Purchases		478	799
Disposals	[1]	(1,753)	(8,613)
Servicing Asset at Amortized Cost, Write-off Related to Sale of Asset		(28,182)	0
Amortization expense		(1,286)	(727)
Balance at end of year		$ 0	$ 28,168

[1] Includes refinancings