ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Classification) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total stockholders' equity	$ 9,820,142	$ 8,795,469	$ 8,566,694	$ 6,909,729
Accumulated Foreign Currency Adjustment Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total stockholders' equity	(311,247)	(217,263)
Accumulated Net Investment Gain (Loss) Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total stockholders' equity	176,563	462,115
AOCI before Tax, Attributable to Parent	185,900	456,100
AOCI before Tax, Attributable to Parent, Taxable	37,400	25,200
Accumulated Other Comprehensive Income (Loss)
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total stockholders' equity	(134,684)	244,852	$ (259,902)	$ 84,729
Net Investment Hedging | Accumulated Foreign Currency Adjustment Attributable to Parent | Euro Senior Notes
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total stockholders' equity	182,600	126,800
AOCI before Tax, Attributable to Parent	310,400	220,500
Net Investment Hedging | Accumulated Foreign Currency Adjustment Attributable to Parent | Foreign Exchange Forward
Accumulated Other Comprehensive Income (Loss) [Line Items]
Total stockholders' equity	(35,000)	(34,800)
AOCI before Tax, Attributable to Parent	(52,600)	(52,600)
The Netherlands | Accumulated Net Investment Gain (Loss) Attributable to Parent
Accumulated Other Comprehensive Income (Loss) [Line Items]
AOCI before Tax, Attributable to Parent, Tax-exempt	$ 148,500	$ 481,300