Payables and Accrued Liabilities - Schedule of Restructuring Reserve by Type of Cost (Details) - USD ($) $ in Thousands	1 Months Ended	11 Months Ended
	Feb. 09, 2018	Dec. 31, 2018
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	$ 16,495	$ 15,925
Charges	931	13,082
Cash payments or other settlements	(1,501)	(11,270)
Balance at end of the period	15,925	17,737
Cumulative charges incurred		73,691
Total expected costs to be incurred		75,325
Severance and Related Costs [Member]
Restructuring Reserve [Roll Forward]
Charges	678	6,856
Cash payments or other settlements	(959)	(7,231)
Cumulative charges incurred		43,567
Office Closures and Other Costs [Member]
Restructuring Reserve [Roll Forward]
Charges	253	6,226
Cash payments or other settlements	(542)	(4,039)
Cumulative charges incurred		30,124
2016 and Prior Actions [Member]
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	540	472
Charges	(2)	(73)
Cash payments or other settlements	(66)	(369)
Balance at end of the period	472	30
Cumulative charges incurred		37,345
Total expected costs to be incurred		37,345
2016 and Prior Actions [Member] | Severance and Related Costs [Member]
Restructuring Reserve [Roll Forward]
Charges	(21)	34
Cash payments or other settlements	0	(127)
Cumulative charges incurred		26,987
2016 and Prior Actions [Member] | Office Closures and Other Costs [Member]
Restructuring Reserve [Roll Forward]
Charges	19	(107)
Cash payments or other settlements	(66)	(242)
Cumulative charges incurred		10,358
2017 Actions [Member]
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	15,955	14,837
Charges	306	1,418
Cash payments or other settlements	(1,424)	(5,020)
Balance at end of the period	14,837	11,235
Cumulative charges incurred		23,982
Total expected costs to be incurred		23,982
2017 Actions [Member] | Severance and Related Costs [Member]
Restructuring Reserve [Roll Forward]
Charges	72	(118)
Cash payments or other settlements	(948)	(1,495)
Cumulative charges incurred		9,013
2017 Actions [Member] | Office Closures and Other Costs [Member]
Restructuring Reserve [Roll Forward]
Charges	234	1,536
Cash payments or other settlements	(476)	(3,525)
Cumulative charges incurred		14,969
2018 Actions [Member]
Restructuring Reserve [Roll Forward]
Balance at beginning of the period	0	616
Charges	627	11,737
Cash payments or other settlements	(11)	(5,881)
Balance at end of the period	616	6,472
Cumulative charges incurred		12,364
Total expected costs to be incurred		13,998
2018 Actions [Member] | Severance and Related Costs [Member]
Restructuring Reserve [Roll Forward]
Charges	627	6,940
Cash payments or other settlements	(11)	(5,609)
Cumulative charges incurred		7,567
2018 Actions [Member] | Office Closures and Other Costs [Member]
Restructuring Reserve [Roll Forward]
Charges	0	4,797
Cash payments or other settlements	$ 0	(272)
Cumulative charges incurred		$ 4,797