Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period			$ 811,850
Accumulated other comprehensive loss at end of period	$ 821,651		821,651
Gains and Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Accumulated other comprehensive loss at beginning of period	(114)	$ (190)	(133)	$ (209)
Losses reclassified from net accumulated other comprehensive loss	19	19	38	38
Net current period other comprehensive income	19	19	38	38
Accumulated other comprehensive loss at end of period	$ (95)	$ (171)	$ (95)	$ (171)