CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 15,953	$ 15,829	$ 31,057	$ 29,653
Other comprehensive (loss) income, net of tax
Unrealized gains (losses) on investment securities arising during the period	6,471	(15,210)	10,333	(18,567)
Change in retirement obligation	237	10,365	474	10,810
Unrealized gain (loss) on derivatives	(637)	690	(1,094)	816
Unrealized gain (loss) on foreign currency exchange	8	(15)	(1)	(27)
Other comprehensive income (loss)	6,079	(4,170)	9,712	(6,968)
Comprehensive income	$ 22,032	$ 11,659	$ 40,769	$ 22,685