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	$ 16,351	$ 19,228	$ 33,380	$ 37,056
Unrealized gains and losses on securities available for sale:
Net unrealized gains (losses) arising during the period	6,339	(12,562)	10,058	(14,182)
Reclassification adjustment for (gains) losses included in net income	(65)	(250)	142	(552)
Total	6,274	(12,812)	10,200	(14,734)
Amortization related to post-retirement obligations	(615)	202	(663)	461
Total other comprehensive income (loss)	5,659	(12,610)	9,537	(14,273)
Total comprehensive income	$ 22,010	$ 6,618	$ 42,917	$ 22,783