Accumulated Other Comprehensive Loss (Textual) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2012
Accumulated Other Comprehensive Loss (Textual) [Abstract]
Net unrealized gains on investment securities-available-for-sale, tax expense	$ 2,232	$ 2,301	$ 2,265
Pension and other postretirement benefits adjustment, tax benefit	$ 18,726	$ 19,058	$ 15,249

Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax Expense

No definition available.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant