Stockholders' Equity - Additional Information (Detail) - USD ($)		3 Months Ended
	May 08, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2014
Stockholders Equity [Line Items]
Common stock, shares issued			91,948,412	91,861,054
Unvested shares of common stock			5,337,118
Treasury stock, shares			6,519,773	6,519,773
Dividends payable			$ 815,000	$ 908,000	$ 21,807,000
Share Repurchase Program, authorized amount						$ 250,000,000
Percentage of common stock outstanding			21.50%
Share Repurchase Program [Member]
Stockholders Equity [Line Items]
Share Repurchase Program, remaining authorized repurchase amount			$ 190,000,000
Stock Repurchase Program, number of shares repurchased			0
Subsequent Event [Member] | Stock Purchase Agreement [Member] | ZHG Group [Member]
Stockholders Equity [Line Items]
Percentage of common stock outstanding	21.00%
Subsequent Event [Member] | Stock Purchase Agreement [Member] | ZHG Group [Member] | Upon Closing of Sale [Member]
Stockholders Equity [Line Items]
Percentage of common stock outstanding	21.00%
Acquisition price paid per share	$ 23.00
2.75x Performance Restricted Shares [Member]
Stockholders Equity [Line Items]
Unvested shares of common stock			1,300,995	1,310,726
Accumulated dividends on unvested performance restricted shares			$ 3,600,000
Dividends payable			$ 0
2.75x Performance Restricted Shares [Member] | Subsequent Event [Member] | Vesting Eligibility Conditions [Member]
Stockholders Equity [Line Items]
Vesting period	12 months
2.75x Modified Performance Restricted Shares [Member] | Scenario, Forecast [Member] | Vesting Upon Closing of Sale [Member]
Stockholders Equity [Line Items]
Accumulated dividends on unvested performance restricted shares		$ 1,300,000