Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended		12 Months Ended
	Sep. 30, 2014		Dec. 31, 2013
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Aggregate fair value of derivative instruments with credit-risk-related contingent features, in case of net liability position	$ 150,909		$ 167,743
Collateral related to the derivatives	128,810		143,540
Fair value of assets required to settle the derivatives in, net liability position	22,099
Amount of unrestricted cash collateral to counterparties in the normal course of business	131,303		143,710
Net derivative gains estimated to be reclassified from accumulated other comprehensive income (loss) into net income within the next twelve months	8,336
Derivative financial instruments
Notional amount	7,662,089		1,492,511
Net derivatives, Fair value	(127,998)		(144,265)
Asset derivatives, Fair value	26,297	[1]	23,478	[1]
Liability derivatives, Fair value	154,295	[1]	167,743	[1]
Average notional amount of the derivative instruments			3,543,173
Interest rate swaps
Derivative financial instruments
Average notional amount of the derivative instruments	329,450		351,579
Other forward contracts
Derivative financial instruments
Average notional amount of the derivative instruments	4,525,207
Cross-currency swaps
Derivative financial instruments
Average notional amount of the derivative instruments	701,202		608,787
Future
Derivative financial instruments
Average notional amount of the derivative instruments	20,807		46,564
Swaption
Derivative financial instruments
Average notional amount of the derivative instruments	432,428		606,374
Derivatives designated as hedges
Derivative financial instruments
Notional amount	436,445		364,745
Net derivatives, Fair value	14,769		10,937
Asset derivatives, Fair value	19,631	[1]	18,927	[1]
Liability derivatives, Fair value	4,862	[1]	7,990	[1]
Derivatives designated as hedges | Cash flow hedges
Derivative financial instruments
Notional amount	358,445		286,745
Net derivatives, Fair value	11,823		5,986
Asset derivatives, Fair value	16,585	[1]	13,829	[1]
Liability derivatives, Fair value	4,762	[1]	7,843	[1]
Derivatives designated as hedges | Cash flow hedges | Interest rate swaps
Derivative financial instruments
Notional amount	184,200		184,200
Net derivatives, Fair value	15,284		13,829
Asset derivatives, Fair value	15,284	[1]	13,829	[1]
Liability derivatives, Fair value	0	[1]	0	[1]
Derivatives designated as hedges | Cash flow hedges | Cross-currency swaps
Derivative financial instruments
Notional amount	174,245		102,545
Net derivatives, Fair value	(3,461)		(7,843)
Asset derivatives, Fair value	1,301	[1]	0	[1]
Liability derivatives, Fair value	4,762	[1]	7,843	[1]
Derivatives designated as hedges | Fair value hedges
Derivative financial instruments
Notional amount	78,000		78,000
Net derivatives, Fair value	2,946		4,951
Asset derivatives, Fair value	3,046	[1]	5,098	[1]
Liability derivatives, Fair value	100	[1]	147	[1]
Derivatives designated as hedges | Fair value hedges | Interest rate swaps
Derivative financial instruments
Notional amount	78,000		78,000
Net derivatives, Fair value	2,946		4,951
Asset derivatives, Fair value	3,046	[1]	5,098	[1]
Liability derivatives, Fair value	100	[1]	147	[1]
Derivatives not designated as hedges
Derivative financial instruments
Notional amount	7,225,644		1,127,766
Net derivatives, Fair value	(142,767)		(155,202)
Asset derivatives, Fair value	6,666	[1]	4,551	[1]
Liability derivatives, Fair value	149,433	[1]	159,753	[1]
Derivatives not designated as hedges | Interest rate swaps
Derivative financial instruments
Notional amount	90,600		55,600
Net derivatives, Fair value	429		(2,038)
Asset derivatives, Fair value	1,840	[1]	1,454	[1]
Liability derivatives, Fair value	1,411	[1]	3,492	[1]
Derivatives not designated as hedges | Futures on equity indices
Derivative financial instruments
Notional amount	7,784		3,483
Net derivatives, Fair value	0		0
Asset derivatives, Fair value	0	[1]	0	[1]
Liability derivatives, Fair value	0	[1]	0	[1]
Derivatives not designated as hedges | Interest rate futures
Derivative financial instruments
Notional amount	20,548		16,233
Net derivatives, Fair value	0		0
Asset derivatives, Fair value	0	[1]	0	[1]
Liability derivatives, Fair value	0	[1]	0	[1]
Derivatives not designated as hedges | Interest rate swaptions
Derivative financial instruments
Notional amount	344,584		494,774
Net derivatives, Fair value	424		1,176
Asset derivatives, Fair value	424	[1]	1,176	[1]
Liability derivatives, Fair value	0	[1]
Derivatives not designated as hedges | Other forward contracts
Derivative financial instruments
Notional amount	6,134,300
Net derivatives, Fair value	(2,087)
Asset derivatives, Fair value	2,347	[1]
Liability derivatives, Fair value	4,434	[1]
Derivatives not designated as hedges | Cross-currency swaps
Derivative financial instruments
Notional amount	627,828		557,676
Net derivatives, Fair value	(141,533)		(154,340)
Asset derivatives, Fair value	2,055	[1]	1,921	[1]
Liability derivatives, Fair value	$ 143,588	[1]	$ 156,261	[1]

[1] The estimated fair value of all derivatives in an asset position is reported within other assets and the estimated fair value of all derivatives in a liability position is reported within other liabilities in the condensed consolidated balance sheets.