Changes in Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Changes in accumulated other comprehensive income by component
Balance at the beginning of the period	$ (11,900)	$ (11,488)
Other comprehensive income before reclassification adjustments	5,847	1,350
Amounts reclassified from accumulated other comprehensive income	(2,042)	163
Other comprehensive income	3,805	1,513
Balance at the end of the period	(8,095)	(9,975)
Income tax expense related to compensation and employee benefits	75	(123)
Unrealized gains and losses on securities available-for-sale
Changes in accumulated other comprehensive income by component
Balance at the beginning of the period	(3,233)	15,853
Other comprehensive income before reclassification adjustments	5,596	670
Amounts reclassified from accumulated other comprehensive income	(1,904)	(66)
Other comprehensive income	3,692	604
Balance at the end of the period	459	16,457
Realized gains (losses) on securities, net of tax	3,122	109
Tax on realized gains on securities	(1,218)	(43)
Change in fair value of interest rate swaps
Changes in accumulated other comprehensive income by component
Balance at the beginning of the period	(5,224)	(8,405)
Other comprehensive income before reclassification adjustments	251	680
Other comprehensive income	251	680
Balance at the end of the period	(4,973)	(7,725)
Change in defined benefit pension plans
Changes in accumulated other comprehensive income by component
Balance at the beginning of the period	(3,443)	(18,936)
Amounts reclassified from accumulated other comprehensive income	(138)	229
Other comprehensive income	(138)	229
Balance at the end of the period	(3,581)	(18,707)
Amortization of prior service cost (compensation and employee benefits)	581	580
Amortization of net loss (compensation and employee benefits)	(368)	(932)
Income tax expense related to compensation and employee benefits	$ (75)	$ 123