Stockholders' Equity (Details 2) - (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at the beginning of the period	$ (15,859)	$ (46,797)
Other comprehensive income before reclassification	(30,706)	42,124
Amount reclassified from accumulated other comprehensive income	(3,878)	(11,186)
Net current period other comprehensive (loss) income	(34,584)	30,938
Balance at the end of the period	(50,443)	(15,859)
Unrealized gains on investment securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at the beginning of the period	3,150	1,823
Other comprehensive income before reclassification	(636)	10,447
Amount reclassified from accumulated other comprehensive income	(3,241)	(9,120)
Net current period other comprehensive (loss) income	(3,877)	1,327
Balance at the end of the period	(727)	3,150
Change in valuation allowance for unrealized gains (losses) on investment securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at the beginning of the period	810	32
Other comprehensive income before reclassification	(381)	6,085
Amount reclassified from accumulated other comprehensive income	(1,900)	(5,307)
Net current period other comprehensive (loss) income	(2,281)	778
Balance at the end of the period	(1,471)	810
Pension and postretirement benefits
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at the beginning of the period	(19,819)	(48,652)
Other comprehensive income before reclassification	(29,689)	25,592
Amount reclassified from accumulated other comprehensive income	1,263	3,241
Net current period other comprehensive (loss) income	(28,426)	28,833
Balance at the end of the period	$ (48,245)	$ (19,819)