Debt - Additional Information (Detail) (USD $)	3 Months Ended		3 Months Ended			3 Months Ended								0 Months Ended	3 Months Ended			3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2014 Revolving credit facility	Mar. 31, 2013 Revolving credit facility	Dec. 31, 2013 Revolving credit facility	Mar. 31, 2014 Revolving credit facility Minimum	Mar. 31, 2014 Revolving credit facility Maximum	Mar. 31, 2014 LIBOR Revolving credit facility	Mar. 31, 2014 Federal Funds Rate Revolving credit facility	Mar. 31, 2014 Prime Rate Revolving credit facility	Mar. 31, 2014 One-month Eurodollar Revolving credit facility	Mar. 31, 2014 One-month Eurodollar Revolving credit facility Minimum	Mar. 31, 2014 One-month Eurodollar Revolving credit facility Maximum	Nov. 30, 2013 Senior Notes [Member] Three Point Two Five Percent Exchangeable Senior Notes [Member]	Mar. 31, 2014 Senior Notes [Member] Three Point Two Five Percent Exchangeable Senior Notes [Member]	Dec. 31, 2013 Senior Notes [Member] Three Point Two Five Percent Exchangeable Senior Notes [Member]	Nov. 21, 2013 Senior Notes [Member] Three Point Two Five Percent Exchangeable Senior Notes [Member]	Mar. 31, 2014 Calendar Quarter After December Thirty One, Twenty Thirteen [Member] Senior Notes [Member] Three Point Two Five Percent Exchangeable Senior Notes [Member] D	Mar. 31, 2014 Period Five Consecutive Business Days [Member] Senior Notes [Member] Three Point Two Five Percent Exchangeable Senior Notes [Member]
Debt Instrument [Line Items]
Senior secured revolving credit facility, current maximum borrowing capacity					$ 380,000,000
Senior secured revolving credit facility, maximum borrowing capacity			500,000,000
Optional one-year extension			1 year
Line of credit facility maturity period	2015-01
Ratio of total indebtedness to total asset value						45.00%	55.00%
Interest rate over LIBOR rate on revolving credit facility						2.50%	3.25%
Description of variable rate basis								LIBOR	Federal Funds Rate	prime rate	one-month Eurodollar
Basis spread on variable rate									0.50%
Basis spread on variable rate, first component											1.00%
Basis spread on variable rate, second component												1.50%	2.25%
Quarterly fee on unused portion of credit facility						0.35%	0.45%
Non utilization fees			200,000	100,000
Amount outstanding under Credit Facility	303,000,000
Weighted average interest rate			2.90%
Amounts available under Credit Facility			32,300,000
Deferred financing costs	5,100,000														3,800,000
Initial exchange rate															0.0469423
Share cap exchange rate															0.0559206
Long-term Debt, Gross														115,000,000.0
Interest rate														3.25%		3.25%
Exchange price per share															$ 21.30
Premium over the last reported sales price of common stock															22.50%
Share Price																	$ 17.39
Percentage of closing sales price per share over current exchange price																		130.00%	98.00%
Trading days																		20
Consecutive trading days																		30 days	5 days
Principal amount, basis for exchange															1,000
Aggregate share cap															19.99%
Long-term Debt														99,100,000
Unamortized discount															15,000,000
Fair value assumptions, interest rate percentage														6.50%
Issuance of exchangeable notes														15,400,000
Financing costs, equity component														500,000
Deferred financing costs, net	$ 5,689,000	$ 6,558,000													$ 3,300,000