Accumulated Other Comprehensive Income - Impact of Reclassifications out of AOCI (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income
Interest expense									$ (230,799)	$ (202,550)	$ (161,104)
Interest income from investment securities									70,848	93,665	112,016
OTTI/Impairment									(728)		(1,056)
Net income	$ 122,721	$ 105,813	$ 112,071	$ 27,046	$ 96,648	$ 117,116	$ 117,640	$ 120,779	367,651	452,183	500,538
Amounts Reclassified from AOCI
Accumulated Other Comprehensive Income
Net income									(9,111)	(1,314)	8,687
Effective Portion of Cumulative Loss on Cash Flow Hedges | Interest rate contracts | Amounts Reclassified from AOCI
Accumulated Other Comprehensive Income
Interest expense									(323)	(741)	(1,372)
Cumulative Unrealized Gain (Loss) on Available-for-Sale Securities | Amounts Reclassified from AOCI
Accumulated Other Comprehensive Income
Interest income from investment securities										5,396
Gain on sale of investments and other assets, net											10,148
OTTI/Impairment											(89)
Net income										5,396	$ 10,059
Foreign Currency Translation | Amounts Reclassified from AOCI
Accumulated Other Comprehensive Income
Gain on sale of investments and other assets, net									(8,788)
Net income									$ (8,788)	(5,969)
Foreign currency loss, net										$ (5,969)