Consolidated Statements of Comprehensive Income (Loss) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013
Statement of Comprehensive Income [Abstract]
Net income, Before-tax Amount	$ 77,024	$ 46,553
Net income, Tax (Expense) Benefit	(28,608)	(16,979)
Net income, Net of Tax Amount	48,416	29,574
Reclassification adjustment for losses (gains) realized in net income, Before-tax Amount	112	112
Reclassification adjustment for losses (gains) realized in net income, Tax (Expense) Benefit	(43)	(43)
Reclassification adjustment for losses (gains) realized in net income, Net of Tax Amount	69	69
Net unrealized gains/losses on investment securities available for sale: Before-tax Amount
Reclassification adjustment for net gains realized in net income, Before-tax Amount	(1,331)	(45)
Net unrealized gains (losses) arising during the period, Before-tax Amount	18,843	(2,164)
Net unrealized gains (losses), Before-tax Amount	17,512	(2,209)
Net unrealized gains/losses on investment securities available for sale: Tax (Expense) Benefit
Reclassification adjustment for net gains realized in net income, Tax (Expense) Benefit	513	16
Net unrealized gains (losses) arising during the period, Tax (Expense) Benefit	(7,255)	833
Net unrealized gains (losses), Tax (Expense) Benefit	(6,742)	849
Net unrealized gains/losses on investment securities available for sale: Net of Tax Amount
Reclassification adjustment for net gains realized in net income, Net of Tax Amount	(818)	(29)
Net unrealized gains (losses) arising during the period, Net of Tax Amount	11,588	(1,331)
Net unrealized gains (losses), Net of Tax Amount	10,770	(1,360)
Post-retirement unfunded health benefit: Before-tax Amount
Reclassification adjustment for (gains) losses realized in net income, Before-tax Amount	(72)	(26)
Post-retirement unfunded health benefit: Tax (Expense) Benefit
Reclassification adjustment for (gains) losses realized in net income, Tax (Expense) Benefit	28	3
Post-retirement unfunded health benefit: Net of Tax Amount
Reclassification adjustment for (gains) losses realized in net income, Net of Tax Amount	(44)	(23)
Other comprehensive (loss) income, Before-tax Amount	17,552	(2,123)
Other comprehensive (loss) income, Tax (Expense) Benefit	(6,757)	809
Other comprehensive (loss) income, Net of Tax Amount	10,795	(1,314)
Comprehensive income, Net of Tax Amount	$ 59,211	$ 28,260