Fair Value of Financial Instruments - Assets measured on a recurring basis (Details) - Fair Value, measurements, recurring - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Other Trading Assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year		$ 1,117	$ 1,590
Included in earnings	[1]	(46)	(154)
Purchases, issuances, sales and settlements: [Abstract]
Balance, end of year		1,071	1,436
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held		(46)	(154)
Equity Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year		253	4
Purchases, issuances, sales and settlements: [Abstract]
Purchases			76
Balance, end of year		253	80
Interest rate contracts
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year		2,874	2,318
Included in earnings	[1]	822	2,669
Purchases, issuances, sales and settlements: [Abstract]
Balance, end of year		3,696	4,987
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held		822	2,669
Other Assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of year		44,541	35,488
Included in earnings	[1]	(8,231)	(3,034)
Purchases, issuances, sales and settlements: [Abstract]
Issuances		4,407	2,759
Balance, end of year		40,717	35,213
Change in unrealized gains (losses) included in earnings for the period, attributable to assets and liabilities still held		$ (8,231)	$ (3,034)

[1] Included in noninterest income in the Unaudited Condensed Consolidated Statements of Income.