Accumulated Other Comprehensive Income (Schedule of Reclassifications) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016
Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net of tax	$ 0
Pension, Postretirement and Other Postemployment Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net of tax	0
Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net of tax	332
Predecessor [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Revenues		$ 428,106
Provision for (benefit from) income taxes		1,111
Net income (loss)		(206,702)
Predecessor [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI before tax		2,672
Predecessor [Member] | Pension, Postretirement and Other Postemployment Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI before tax		1,338
Provision for (benefit from) income taxes		(481)
Net of tax		857
Predecessor [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI before tax		1,334
Predecessor [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Revenues		226
Provision for (benefit from) income taxes		(82)
Net income (loss)		144
Predecessor [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and investment income		(2,895)
Provision for (benefit from) income taxes		1,038
Net income (loss)		$ (1,857)
Successor [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Revenues	600,975
Provision for (benefit from) income taxes	(840)
Net income (loss)	51,668
Successor [Member] | Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI before tax	0
Successor [Member] | Pension, Postretirement and Other Postemployment Benefits [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI before tax	0
Provision for (benefit from) income taxes	0
Net of tax	0
Successor [Member] | Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification from AOCI before tax	0
Successor [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Derivative Instruments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Revenues	0
Provision for (benefit from) income taxes	0
Net income (loss)	0
Successor [Member] | Reclassification out of Accumulated Other Comprehensive Income [Member] | Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Interest and investment income	332
Provision for (benefit from) income taxes	0
Net income (loss)	$ 332