CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 14,911	$ 16,242	$ 44,564	$ 51,038
Other comprehensive (loss) income, net of tax
Unrealized gains (losses) on investment securities arising during the period	(4,003)	(934)	(22,570)	1,662
Change in retirement obligation	1,166	419	11,976	1,129
Unrealized gain (loss) on derivatives	(818)	(182)	(2)	(182)
Unrealized gain (loss) on foreign currency exchange	6	14	(21)	26
Other comprehensive income (loss)	(3,649)	(683)	(10,617)	2,635
Comprehensive income	$ 11,262	$ 15,559	$ 33,947	$ 53,673