Organization and Basis of Presentation - Accumulated Other Comprehensive Income Summary (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2016 USD ($)
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	$ 6,237,733
Balance at period end	6,141,992
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	(42,011)
Other comprehensive income (loss) before reclassification	(4,137)
Amounts reclassified from accumulated other comprehensive loss	1,999
Other comprehensive loss	(2,138)
Balance at period end	(44,149)
Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	(48,366)
Other comprehensive income (loss) before reclassification	(4,444)
Amounts reclassified from accumulated other comprehensive loss	1,999
Other comprehensive loss	(2,445)
Balance at period end	(50,811)
Accumulated Net Investment Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Balance at period beginning	6,355
Other comprehensive income (loss) before reclassification	307
Amounts reclassified from accumulated other comprehensive loss	0
Other comprehensive loss	307
Balance at period end	$ 6,662