Equity Incentive Compensation Plans and Other Employee Benefits - Non-Cash Stock-Based Compensation Cost Related to Equity Awards (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Stock Based Compensation [Line Items]
Non-cash stock based compensation	$ 7,226	$ 8,289	$ 11,941
Common Stock Options [Member]
Stock Based Compensation [Line Items]
Non-cash stock based compensation	0	0	69
Nonvested Common Stock [Member]
Stock Based Compensation [Line Items]
Non-cash stock based compensation	6,036	5,852	6,696
Nonvested Equity Common Stock Units [Member]
Stock Based Compensation [Line Items]
Non-cash stock based compensation	1,138	690	883
Nonvested Performance-Based Equity [Member]
Stock Based Compensation [Line Items]
Non-cash stock based compensation	0	558	1,808
Nonvested Performance Cash Units [Member]
Stock Based Compensation [Line Items]
Cash Unit Based Compensation Awards	$ 52	$ 1,189	$ 2,485