Subsequent Events (Detail) - USD ($)					3 Months Ended				12 Months Ended
	Feb. 24, 2017	Feb. 15, 2017	Feb. 06, 2017	Feb. 01, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Feb. 01, 2020	Feb. 07, 2017	Dec. 16, 2016
Subsequent Event [Line Items]
Common stock dividends declared (in $ per share)					$ 0.45	$ 0.45	$ 0.45	$ 0.45	$ 1.8	$ 1.8	$ 1.35
Term loan [Member] | Loan Facility [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity														$ 475,000,000.0
Revolving credit facility [Member] | Loan Facility [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity														$ 100,000,000.0
Revolving credit facility [Member] | Credit Facility [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity						$ 150,000,000.0
Subsequent event [Member]
Subsequent Event [Line Items]
Net proceeds from stock issuance				$ 207,100,000
Common stock dividends declared (in $ per share)		$ 0.45
Subsequent event [Member] | Common stock [Member]
Subsequent Event [Line Items]
Stock issued (in shares)				910,000
Net proceeds from stock issuance				$ 207,100,000
Subsequent event [Member] | Convertible preferred stock [Member]
Subsequent Event [Line Items]
Stock issued (in shares)				1,150,000
Preferred stock dividend rate				7.25%
Preferred stock liquidation preference (in $ per share)	$ 100			$ 100.00
Preferred stock conversion, threshold consecutive trading days				20 days
Preferred stock dividends declared (in $ per share)		$ 1.8125
Subsequent event [Member] | Underwriters option [Member] | Common stock [Member]
Subsequent Event [Line Items]
Stock issued (in shares)	136,500
Net proceeds from stock issuance	$ 14,300,000
Subsequent event [Member] | Forecast [Member] | Underwriters option [Member] | Common stock [Member]
Subsequent Event [Line Items]
Stock issued (in shares)	136,500
Subsequent event [Member] | Minimum [Member] | Forecast [Member] | Convertible preferred stock [Member]
Subsequent Event [Line Items]
Preferred stock, shares issuable upon conversion (in shares)												0.7576
Subsequent event [Member] | Maximum [Member] | Forecast [Member] | Convertible preferred stock [Member]
Subsequent Event [Line Items]
Preferred stock, shares issuable upon conversion (in shares)												0.9091
Subsequent event [Member] | Term loan [Member] | Loan Facility [Member]
Subsequent Event [Line Items]
Maximum borrowing capacity													$ 260,000,000.0
Subsequent event [Member] | Revolving credit facility [Member] | Credit Facility [Member]
Subsequent Event [Line Items]
Repayment of debt			$ 30,000,000