Consolidated Statements of Comprehensive Income (Loss) (USD $) In Thousands, unless otherwise specified	3 Months Ended				9 Months Ended
	Sep. 30, 2012		Sep. 30, 2011		Sep. 30, 2012		Sep. 30, 2011
Statement of Income and Comprehensive Income [Abstract]
Net income (loss), Before-tax Amount	$ 30,514		$ 37,118		$ 103,777		$ (86,510)
Net income (loss), Tax (Expense) Benefit	211		(6,910)		2,393		(1,690)
Net income (loss), Net of Tax Amount	30,725		30,208		106,170		(88,200)
Net unrealized gains/losses on cash flow hedges: Before-tax Amount
Net unrealized gains (losses) arising during the period, Before-tax Amount	49		(2,504)		(1,492)		(9,478)
Valuation allowance for the change in deferred taxes arising from unrealized gains/losses, Before-tax Amount	0	[1]	0	[1]	0	[1]	0	[1]
Net unrealized gains (losses), Before-tax Amount	49		(2,504)		(1,492)		(9,478)
Net unrealized gains/losses on cash flow hedges: Tax (Expense) Benefit
Net unrealized gains (losses) arising during the period, Tax (Expense) Benefit	(19)		974		575		3,588
Valuation allowance for the change in deferred taxes arising from unrealized gains/losses, Tax (Expense) Benefit	33	[1]	(3,561)	[1]	(575)	[1]	(3,561)	[1]
Net unrealized gains (losses), Tax (Expense) Benefit	14		(2,587)		0		27
Net unrealized gains/losses on cash flow hedges: Net of Tax Amount
Net unrealized gains (losses) arising during the period, Net of Tax Amount	30		(1,530)		(917)		(5,890)
Valuation allowance for the change in deferred taxes arising from unrealized gains/losses, Net of Tax Amount	33	[1]	(3,561)	[1]	(575)	[1]	(3,561)	[1]
Net unrealized gains (losses), Net of Tax Amount	63		(5,091)		(1,492)		(9,451)
Net unrealized gains/losses on investment securities available for sale: Before-tax Amount
Net unrealized gains (losses) arising during the period, Before-tax Amount	15,772		26,706		26,848		49,169
Reclassification adjustment for (gains) losses realized in net income, Tax (Expense) Benefit	(6,656)		(62,873)		(30,909)		(64,670)
Valuation allowance for the change in deferred taxes arising from unrealized gains/losses, Before-tax Amount	0	[1]	0	[1]	0	[1]	0	[1]
Net unrealized gains (losses), Before-tax Amount	9,116		(36,167)		(4,061)		(15,501)
Net unrealized gains/losses on investment securities available for sale: Tax (Expense) Benefit
Net unrealized gains (losses) arising during the period, Tax (Expense) Benefit	(6,069)		(10,282)		(10,333)		(18,533)
Other Comprehensive Income (Loss), Reclassification Adjustment for Sale of Securities Included in Net Income, Tax	2,563		24,207		11,900		24,899
Valuation allowance for the change in deferred taxes arising from unrealized gains/losses, Tax (Expense) Benefit	3,506	[1]	(6,383)	[1]	(1,567)	[1]	(6,383)	[1]
Net unrealized gains (losses), Tax (Expense) Benefit	0		7,542		0		(17)
Net unrealized gains/losses on investment securities available for sale: Net of Tax Amount
Net unrealized gains (losses) arising during the period, Net of Tax Amount	9,703		16,424		16,515		30,636
Reclassification adjustment for (gains) losses realized in net income, Net of Tax Amount	(4,093)		(38,666)		(19,009)		(39,771)
Valuation allowance for the change in deferred taxes arising from unrealized gains/losses, Net of Tax Amount	3,506	[1]	(6,383)	[1]	(1,567)	[1]	(6,383)	[1]
Net unrealized gains (losses), Net of Tax Amount	9,116		(28,625)		(4,061)		(15,518)
Amortization of post-retirement unfunded health benefit: Before-tax Amount
Amortization arising during the period, Before-tax Amount	(26)		0		616		0
Valuation allowance for the change in deferred taxes arising from amortization, Before-tax Amount	0		0		0		0
Net amortization, Before-tax Amount	(26)		0		616		0
Amortization of post-retirement unfunded health benefit: Tax (Expense) Benefit
Amortization arising during the period, Tax (Expense) Benefit	10		0		(237)		0
Valuation allowance for the change in deferred taxes arising from amortization, Tax (Expense) Benefit	(10)		0		237		0
Net amortization, Tax (Expense) Benefit	0		0		0		0
Amortization of post-retirement unfunded health benefit: Net of Tax Amount
Amortization arising during the period, Net of Tax Amount	(16)		0		379		0
Valuation allowance for the change in deferred taxes arising from amortization, Net of Tax Amount	(10)		0		237		0
Net amortization, Net of Tax Amount	(26)		0		616		0
Other comprehensive income (loss), Before-tax Amount	9,139		(38,671)		(4,937)		(24,979)
Less: comprehensive loss attributable to non-controlling interest, Before-tax Amount	0		0		0		(220)
Comprehensive income (loss), Before-tax Amount	39,653		(1,553)		98,840		(111,269)
Other comprehensive income (loss), Tax (Expense) Benefit	(14)		(4,955)		0		(10)
Less: comprehensive loss attributable to non-controlling interest, Tax (Expense) Benefit	0		0		0		0
Comprehensive income (loss), Tax (Expense) Benefit	225		(1,955)		2,393		(1,680)
Other comprehensive income (loss), Net of Tax Amount	9,153		(33,716)		(4,937)		(24,969)
Less: comprehensive loss attributable to non-controlling interest, Net of Tax Amount	0		0		0		(220)
Comprehensive income (loss), Net of Tax Amount	$ 39,878		$ (3,508)		$ 101,233		$ (112,949)

[1] In accordance with ASC 740-20-45-11(b), the deferred tax asset valuation allowance associated with unrealized gains and losses not recognized in income is charged directly to other comprehensive income (loss).