Schedule I - Dividends from Subsidiary - Schedule of Quarterly Cash Dividends to Common Stockholders (Detail) - $ / shares	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Dividends Payable [Line Items]
Cash dividends declared per share	$ 0.73	$ 0.84
Q4 2015 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date	Jan. 15, 2016
Cash dividends payable date	Jan. 22, 2016
Cash dividends declared per share	$ 0.21
Q1 2016 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date	Mar. 14, 2016
Cash dividends payable date	Apr. 01, 2016
Cash dividends declared per share	$ 0.21
Q2 2016 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date	Jun. 20, 2016
Cash dividends payable date	Jul. 01, 2016
Cash dividends declared per share	$ 0.21
Q3 2016 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date	Sep. 29, 2016
Cash dividends payable date	Oct. 07, 2016
Cash dividends declared per share	$ 0.10
Q4 2014 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date		Jan. 13, 2015
Cash dividends payable date		Jan. 22, 2015
Cash dividends declared per share		$ 0.21
Q1 2015 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date		Mar. 13, 2015
Cash dividends payable date		Apr. 01, 2015
Cash dividends declared per share		$ 0.21
Q2 2015 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date		Jun. 22, 2015
Cash dividends payable date		Jul. 01, 2015
Cash dividends declared per share		$ 0.21
Q3 2015 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date		Sep. 29, 2015
Cash dividends payable date		Oct. 06, 2015
Cash dividends declared per share		$ 0.21
Parent Company [Member] | Q4 2015 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date	Jan. 15, 2016
Cash dividends payable date	Jan. 22, 2016
Cash dividends declared per share	$ 0.21
Parent Company [Member] | Q1 2016 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date	Mar. 14, 2016
Cash dividends payable date	Apr. 01, 2016
Cash dividends declared per share	$ 0.21
Parent Company [Member] | Q2 2016 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date	Jun. 20, 2016
Cash dividends payable date	Jul. 01, 2016
Cash dividends declared per share	$ 0.21
Parent Company [Member] | Q3 2016 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date	Sep. 29, 2016
Cash dividends payable date	Oct. 07, 2016
Cash dividends declared per share	$ 0.10
Parent Company [Member] | Q4 2014 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date		Jan. 13, 2015
Cash dividends payable date		Jan. 22, 2015
Cash dividends declared per share		$ 0.21
Parent Company [Member] | Q1 2015 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date		Mar. 13, 2015
Cash dividends payable date		Apr. 01, 2015
Cash dividends declared per share		$ 0.21
Parent Company [Member] | Q2 2015 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date		Jun. 22, 2015
Cash dividends payable date		Jul. 01, 2015
Cash dividends declared per share		$ 0.21
Parent Company [Member] | Q3 2015 Declaration [Member]
Dividends Payable [Line Items]
Cash dividends record date		Sep. 29, 2015
Cash dividends payable date		Oct. 06, 2015
Cash dividends declared per share		$ 0.21